Hi all,
An explanation of these various problems, and a simple solution, is below.
I had a lot of hassle with trying to solve these five problems:
1 - Trying to mount an external hard drive, crashes the mac.
2 - The external hard drive fails to mount, (but doesn't crash the mac).
3 - Trying to mount a second external hard drive, crashes the mac.
4 - The mac fails to mount a second external hard drive, (but trying to mount the second external hard drive does not crash the mac).
5 - There were also problems with usb 2.0 self-powered devices (e.g., printer and dvd burner) not connecting to the mac. (By 'self-powered', i mean any devices that require their own power supply.)
There is a simple solution to all of this, and hopefully this solution will help some people.
If you want to skip straight to the solution, then just scroll down to the section called “The solution”.
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The situation/setup
I have two anker 14-port usb hubs, (these are the usb hubs which have 13 ports for data transfer, and one port for charging). I only use the 13 usb ports for data transfer, (i do not use the charging port). Each hub plugs into a separate usb 3.0 port on my mac, (i.e., I'm not daisy-chaining these two hubs.)
The first anker hub has all of my usb 2.0 devices connected to it, (e.g., keyboard, mouse, dvd burner, etc).
The second anker hub has all of my usb 3.0 devices connected to it, (e.g., external hard drives, pen drives, etc). Each of my external hard drives has it's own power supply, and each hard drive is connected in parallel to the anker hub, (i.e., the external hard drives are not daisy-chained). For normal everyday use, I must be able to use two external hard drives simultaneously.
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Details of the five problems
With both hubs connected, then after i switch on the mac, the computer boots up fine, and all of the usb 2.0 devices work perfectly, but when i power up one of the external hard drives, then there are five common outcomes:
1 - The mac crashes. The crash happens on the instant that i switch on the power supply to the first external hard drive.
2 - After switching on the power supply to the first external hard drive, the mac doesn't crash, but the external hard drive doesn't mount. The external hard drive is not visible in finder, nor in disk utility. It does not show anywhere.
3 - One external hard drive has mounted, but the mac crashes if i try to mount the second external hard drive. The mac crashes as soon as i switch on the power supply to the second external hard drive. I.e., there is the rare occasion when one external hard drive will mount, however, the problem is that (throughout most of the day) i need to use 2 external hard drives (at the same time), and therefore being able to mount only one external hard drive, is not good enough. So i try to mount the second external hard drive, and it crashes the mac.
4 - The mac won't mount the second external hard drive. I.e., on the rare occasion when one external hard drive will mount, the mac fails to mount the second external hard drive, (but the mac doesn't crash when i switch on the power supply to the second external hard drive). As explained in point 3, i need to use two external hard drivers simultaneously, and so not being able to mount the second external hard drive, makes this situation unacceptable.
5 - There were also problems with usb 2.0 self-powered devices (e.g., printer and dvd burner) not connecting to the mac.
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Tests
Test 1:
If i disconnect the first hub (which has all the usb 2.0 devices) and then boot the mac, then the other hub will work perfectly. I.e., I can mount two external hard drives simultaneously, and the mac doesn't crash.
Test 2:
If i disconnect the second hub (which has external hard drives connected) and then boot the mac, then the other hub will work perfectly. I.e., the hub will run all of the usb 2.0 devices perfectly, and the mac doesn't crash.
Test 3:
If i have both hubs plugged into the mac, and whilst the computer is off, i turn on the power to one of the external hard drives, and then i switch on the mac, then the computer will boot up normally, and the external hard drive will mount, but some usb 2.0 devices will fail to work.
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Conclusion (about what is causing these five problems)
The conclusion that I've come to, is that:
The five problems that I'm having (which are explained above), only exist when more than one usb 3.0 hub is used at the same time. This is true not just for the anker hubs, but also for the other usb 3.0 hubs that i have tried.
Note: Some of these problems may also occur when more than one usb 3.0 self-powered devices are connected directly to the mac, and are used at the same time, (e.g., two usb 3.0 self-powered external hard drives, plugged directly into the mac).
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The solution
I added a usb 2.0 extension cable (15 cm long), onto the end of the first usb hub (which has all of my usb 2.0 devices plugged into it). The second usb hub (which has all of my usb 3.0 devices connected to it), is just plugged directly into the mac (as normal), and so that hub gets usb 3.0 speeds.
I.e., with the first usb hub, I still have the original usb 3.0 cable that came with the anker hub (which goes from the hub to the mac), but on the end of this i attached a usb 2.0 extension cable (15 cm long), and this then goes into the usb 3.0 port on my mac.
What this means, is that when i have both anker hubs connected to my mac, this usb 2.0 extension cable forces the mac to read/recognise one of the hubs as being a usb 2.0 hub, and therefore the mac only has to contend with one usb 3.0 hub, and this somehow solves all of the problems.
After adding the usb 2.0 extension cable (15 cm long), i did an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then i reset the nvram. I don't know if i needed to do these three things, but i just did it for good measure.
Immediately after adding this solution (of the usb 2.0 extension cable), all of the usb 2.0 devices are working, and all of the usb 3.0 devices are working (and are running at usb 3.0 speeds). I am now able to use both of my external hard drives simultaneously, along with all the other devices.
I implemented this solution one week ago (with three usb 3.0 hubs (explained below)), and i have had no problems (of any kind) over this past week. I deliberately waited one week (before posting this solution), to see if all the problems were truly solved. And it appears that all problems have been truly solved.
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Notes:
I have used this 15 cm usb 2.0 extension cable, but i presume that other lengths will work. I just wanted to keep it as short as possible. (15 cm is roughly 6 inches, and this is usually the shortest length available.) There are many reasons for wanting to keep it as short as possible, and one of these is because i read somewhere, that it's best to try to keep the length of the usb hub's cable (from the usb hub to the computer) to a maximum length of 1 metre.
Since my mac has 4 usb ports, i presume that i could add 2 more usb hubs, as long as i also apply the same solution. I.e., my guess is that the mac can handle 4 hubs, as long as 3 of those hubs are recognised as usb 2.0.
I.e., my guess about this whole issue, is that the mac can only deal with one usb 3.0 hub.
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Confirmation test - that I can connect three usb 3.0 hubs (if this solution is used)
To test this hypothesis further (i.e., that the mac can only deal with one usb 3.0 hub), i tested the following setup:
Hub 1:
14-port anker usb 3.0 hub (with the solution of the usb 2.0 extension cable (15 cm long). I only have usb 2.0 devices plugged into this hub.
Hub 2:
10-port technet usb 3.0 hub. This usb hub is plugged directly into my mac (as normal). I have all my usb 3.0 devices plugged into it, and they run at usb 3.0 speeds.
Hub 3:
14-port anker usb 3.0 hub (with the solution of the usb 2.0 extension cable (15 cm long). I only have usb 2.0 devices plugged into this hub.
All three hubs are plugged into the mac in parallel, (i.e., none of them are daisy-chained). To be more exact, I have four usb 3.0 ports on my mac, and I have plugged the technet into the port on the far left, and the two anker hubs are plugged into the ports on the right.
Since implementing this solution (about a week ago), all of my usb devices have been working perfectly. There have been times when I have had the mac on for over 24 hours, and the usb devices still all work fine, (i mention this because before implementing this solution, there were times when the problem would get worse after 20 hours, or after many restarts).
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Exact details, and why a usb 2.0 hub is perhaps not a good solution (as compared to this solution)
I will now be a bit more specific, because sometimes that is necessary. E.g., the solution of adding a usb 2.0 extension cable, to this specific hub, does work (for me), but perhaps if i bought a usb 2.0 hub, and plugged it directly into my mac, then there might be all types of problems.
Indeed, perhaps the combination of a specific usb 3.0 hub, and this solution, does work, whereas a usb 2.0 hub might not work, because there are many usb 2.0 hubs that are using a bad/poor quality:
- chipset
- firmware
- power supply
- etc
and if any one of these is bad/poor quality, then that can cause any number of problems.
So, to be more exact about the chipset (and firmware, and power supply) of the two hubs, (that i have mentioned above), i will copy and paste the hub's title/description:
Anker AH241 USB 3.0 Aluminum 13-Port Hub + 5V 2.1A Smart Charging Port with 12V 5A Power Adapter [VIA VL812-B2 Chipset]
TeckNet HU10 USB 3.0 10 Port Hub with 48W Power Adapter and 3ft USB 3.0 Cable [VIA VL812 Chipset]
On my mac, when i check the system report (via: about this mac > system report > usb), i can see that the manufacturer and version is:
for the technet hub:
Manufacturer: VIA Labs, Inc.
Version: 90.81
for the anker hub:
Manufacturer: VIA Labs, Inc.
Version: b.e0 (Note: “Version: b.e0” , is what it shows after i add the usb 2.0 extension cable. Without this usb 2.0 extension cable, i think that it used to say “Version: b.e1”). This was true for both anker hubs.)
Before buying the anker hubs, I spoke to anker support, and they said that this anker hub uses the same firmware as their 10-port hub. (Their 10-port hub is advertised as using firmware 9081, which i'm guessing is the same as 90.81)
I have read somewhere that to avoid problematic usb 3.0 hubs, the firmware must be above 90.xx
I should add that have no affiliation with either of these two companies. The only reasons why i bought these hubs, is because i like to buy the largest hub possible (i.e., the one with the most data transfer ports), and one which has good reviews, and one which openly states what chipset they are using, and that it has a decent power supply. I also prefer hubs which only have data transfer ports, (because i don't use the charging ports, and the more things/features that the manufacturer adds to a usb hub, the more chances there are of problems occurring).
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Solutions that I tried (previously), which did not solve the five problems
Before finding this solution (of adding the 15cm usb 2.0 extension cable), i tried other ways to solve these five problems. I am listing these various attempted solutions below, because i have left these solution in place. I.e., they might (or might not) also be a part of the solution, and/or they might be of help to some people.
The things that i tried are as follows:
1 - Restart the mac.
2 - Do an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then reset the nvram.
3 - Try to plug the hubs into different ports of the mac, and then after each of these changes, do an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then i reset the nvram. No matter which ports i used to plug in the usb hubs, the problems remained (especially in the long term, i.e., after a few reboots). I.e., occasionally doing these 3 resets did help, but only in the short term, (i.e., the problem resurfaced again after subsequent reboots). Many times it did not even help on that one occasion (on the first boot) after doing these 3 resets.
4 - Run “First Aid” (via disk utility) on each of the external hard drives, (including each separate volume on each external hard drive).
5 - When using any of the usb hubs, i have made sure that the ports are used in order. I did this because i did read somewhere that some people found that there were issues with usb hubs, if they left empty ports in between used ports. Ie, start by using port number 1, 2, 3, etc, and fill up the hub in that fashion. I'm not sure if this helps, but it doesn't hurt to do it like this, and there is some logic to making sure that it's done in this way.
(The first port in the hub (port number 1), is usually the port nearest to the end from which the hub's usb cable goes from the hub to the computer.)
6 - In addition to the previous point, there is also perhaps another issue, which is that it's best to keep the devices which are always active, plugged into the hub nearer to the first port (port number 1). Ie, sometimes a usb hub has many devices (and extension cables) plugged into it, but many of them are not active, and if there are too many inactive devices (or extension cables) in a row, then the devices plugged in after this, will not be active.
The reason for this, might be because the usb hub is divided into sections, (e.g., 4 ports per section), and therefore if one section is not active, then the subsequent sections are also not active. Or, perhaps it's because within one section, the first port of that section must be active, for that section to be active.
I don't know if what i've just explained (in the previous paragraph), is always true (or true at all), but i have come across issues like this myself, where after plugging in all the devices into the hub, one device is not working/recognised (but all the other devices are working/recognised), and so according to the above information, i changed the order in which i plugged the devices into the hub, and that did solve the problem (of that one device not working/recognised).
7 - I have excluded spotlight from searching each of my external hard drives.
Despite the fact that this did not solve the original five problems, i have still decided to always excluded spotlight from searching each of my external hard drives, and i now use an app called “EasyFind” to search for files/folders.
8 - I have excluded my antivirus from accessing each of my external hard drives. (This was done in the bitdefender antivirus app.)
Note: I found that to use bitdefender, i had to immediately exclude all external hard drives, because if i did not do this, then the external hard drives would not unmount, (because bitdefender was still wanting access to them, which prevents the unmount from happening). This is done in the bitdefender app, (via: preferences > exclusions).
9 - Alter the preferences in finder, (via: finder preferences > general).
10 - Relaunch finder.
11 - Run an antivirus scan (via bitdefender).
12 - Run a scan for other types of adware (via malwarebytes - anti-malware).
13 - My external hard drives (seagate backup plus desktop) came with some seagate software, but i don't install this software, (because these types of software just add problems, and aren't needed).
14 - My external hard drives are formatted in hfs+, and therefore there is nothing more i can do in respect to that. (I.e., other types of formats could be the cause of problems, for various reasons.)
15 - I have uninstalled virtualbox (in case that was causing the problem). I do not have any virtual machines running on my mac.
16 - I read somewhere something about the “usb overdrive” app, but i do not have this app on my mac (so i did not need to experiment with uninstalling it). I don't know if this would be an issue, because I use the “keyboard maestro” app, and this is always running in the background of my mac.
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Details about the problem of usb 2.0 self-powered devices not connecting to the mac
When i switched on my printer or dvd burner (which was connected via a usb cable), it would sometimes not connect to the mac. Later on i realised that the “sometimes” depended on what other self-powered usb devices were already actively being used on the mac.
The reason why this is important to mention, is because the printer and dvd burner are usb 2.0 devices, and therefore this means that this problem (of the mac having many issues, as soon as more than one usb 3.0 hub was connected to the mac), is not just about usb 3.0 devices.
I.e., this problem was not just causing issues with usb 3.0 devices (e.g., my external hard drives), but also any self-powered usb 2.0 devices (e.g., printers, dvd burners, etc). (By “self-powered”, i mean any devices that require their own power supply.)
Perhaps this means that whenever i had two usb 3.0 hubs connected to my mac (without the 15cm usb 2.0 extension cable), that then there were issues with the mac in regards to only being able to run a maximum of “x” number of active self-powered usb devices (regardless of whether they were usb 2.0 or usb 3.0 devices).
And this maximum number (“x”) included: external hard drives (which have their own power supply), printers (which were connected via usb cable), dvd burners (which were connected via usb cable, and have their own power supply), etc. And, this might also include all the usb hubs (which have their own power supply). But it (obviously) only includes the devices that were powered up.
After implementing the solution (of adding a 15cm usb 2.0 extension cable, onto two of the three usb 3.0 hubs), i seem to be able to connect as many usb 2.0 and 3.0 devices as i want, whether they're self-powered, or not. I presume that there must be some limit (to the number of devices that can be connected to the mac), but i haven't hit that limit yet (and hopefully never will).
I.e., it really seems as though the conclusion is that: As long as no more than one usb 3.0 hub is attached to the mac, then everything is fine (for all usb 2.0 and 3.0 devices).
But I'm not sure if this is also true for other usb 3.0 self-powered devices. I.e., are there similar problems as soon as more than one usb 3.0 self-powered device is attached directly to the mac? I say this because I presume that any self-powered usb device has a chipset (or whatever it's called) inside it, (just as the usb 3.0 hub does), and therefore the same problems could be caused.
And/or, perhaps this also applies to any devices that have these certain types of chipsets in them, (whether the device is self-powered, or not).
Anyhow, I've spent far too long on all of this, and so I'm not going to examine this issue any further.
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Note: Since the manufacturers (of these usb 3.0 hubs) do say that these hubs are backwards compatible with computers which have usb 2.0 ports, then this means that you can plug these usb 3.0 hubs into computers that have usb 2.0 ports. The point is, that since the manufacturers say this, this probably means that it's also safe to add a 15 cm usb 2.0 extension cable.
And this is probably more true, if you're using the original usb cable that came with the hub, or you're making sure that the cable (which runs from the usb hub to the mac) is not longer than 1 metre. However, all of this is just my take on the situation, (and I'm no expert).
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I hope this helps a few people, because otherwise I've just wasted a lot of time writing all of this...
An explanation of these various problems, and a simple solution, is below.
I had a lot of hassle with trying to solve these five problems:
1 - Trying to mount an external hard drive, crashes the mac.
2 - The external hard drive fails to mount, (but doesn't crash the mac).
3 - Trying to mount a second external hard drive, crashes the mac.
4 - The mac fails to mount a second external hard drive, (but trying to mount the second external hard drive does not crash the mac).
5 - There were also problems with usb 2.0 self-powered devices (e.g., printer and dvd burner) not connecting to the mac. (By 'self-powered', i mean any devices that require their own power supply.)
There is a simple solution to all of this, and hopefully this solution will help some people.
If you want to skip straight to the solution, then just scroll down to the section called “The solution”.
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The situation/setup
I have two anker 14-port usb hubs, (these are the usb hubs which have 13 ports for data transfer, and one port for charging). I only use the 13 usb ports for data transfer, (i do not use the charging port). Each hub plugs into a separate usb 3.0 port on my mac, (i.e., I'm not daisy-chaining these two hubs.)
The first anker hub has all of my usb 2.0 devices connected to it, (e.g., keyboard, mouse, dvd burner, etc).
The second anker hub has all of my usb 3.0 devices connected to it, (e.g., external hard drives, pen drives, etc). Each of my external hard drives has it's own power supply, and each hard drive is connected in parallel to the anker hub, (i.e., the external hard drives are not daisy-chained). For normal everyday use, I must be able to use two external hard drives simultaneously.
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Details of the five problems
With both hubs connected, then after i switch on the mac, the computer boots up fine, and all of the usb 2.0 devices work perfectly, but when i power up one of the external hard drives, then there are five common outcomes:
1 - The mac crashes. The crash happens on the instant that i switch on the power supply to the first external hard drive.
2 - After switching on the power supply to the first external hard drive, the mac doesn't crash, but the external hard drive doesn't mount. The external hard drive is not visible in finder, nor in disk utility. It does not show anywhere.
3 - One external hard drive has mounted, but the mac crashes if i try to mount the second external hard drive. The mac crashes as soon as i switch on the power supply to the second external hard drive. I.e., there is the rare occasion when one external hard drive will mount, however, the problem is that (throughout most of the day) i need to use 2 external hard drives (at the same time), and therefore being able to mount only one external hard drive, is not good enough. So i try to mount the second external hard drive, and it crashes the mac.
4 - The mac won't mount the second external hard drive. I.e., on the rare occasion when one external hard drive will mount, the mac fails to mount the second external hard drive, (but the mac doesn't crash when i switch on the power supply to the second external hard drive). As explained in point 3, i need to use two external hard drivers simultaneously, and so not being able to mount the second external hard drive, makes this situation unacceptable.
5 - There were also problems with usb 2.0 self-powered devices (e.g., printer and dvd burner) not connecting to the mac.
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Tests
Test 1:
If i disconnect the first hub (which has all the usb 2.0 devices) and then boot the mac, then the other hub will work perfectly. I.e., I can mount two external hard drives simultaneously, and the mac doesn't crash.
Test 2:
If i disconnect the second hub (which has external hard drives connected) and then boot the mac, then the other hub will work perfectly. I.e., the hub will run all of the usb 2.0 devices perfectly, and the mac doesn't crash.
Test 3:
If i have both hubs plugged into the mac, and whilst the computer is off, i turn on the power to one of the external hard drives, and then i switch on the mac, then the computer will boot up normally, and the external hard drive will mount, but some usb 2.0 devices will fail to work.
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Conclusion (about what is causing these five problems)
The conclusion that I've come to, is that:
The five problems that I'm having (which are explained above), only exist when more than one usb 3.0 hub is used at the same time. This is true not just for the anker hubs, but also for the other usb 3.0 hubs that i have tried.
Note: Some of these problems may also occur when more than one usb 3.0 self-powered devices are connected directly to the mac, and are used at the same time, (e.g., two usb 3.0 self-powered external hard drives, plugged directly into the mac).
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The solution
I added a usb 2.0 extension cable (15 cm long), onto the end of the first usb hub (which has all of my usb 2.0 devices plugged into it). The second usb hub (which has all of my usb 3.0 devices connected to it), is just plugged directly into the mac (as normal), and so that hub gets usb 3.0 speeds.
I.e., with the first usb hub, I still have the original usb 3.0 cable that came with the anker hub (which goes from the hub to the mac), but on the end of this i attached a usb 2.0 extension cable (15 cm long), and this then goes into the usb 3.0 port on my mac.
What this means, is that when i have both anker hubs connected to my mac, this usb 2.0 extension cable forces the mac to read/recognise one of the hubs as being a usb 2.0 hub, and therefore the mac only has to contend with one usb 3.0 hub, and this somehow solves all of the problems.
After adding the usb 2.0 extension cable (15 cm long), i did an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then i reset the nvram. I don't know if i needed to do these three things, but i just did it for good measure.
Immediately after adding this solution (of the usb 2.0 extension cable), all of the usb 2.0 devices are working, and all of the usb 3.0 devices are working (and are running at usb 3.0 speeds). I am now able to use both of my external hard drives simultaneously, along with all the other devices.
I implemented this solution one week ago (with three usb 3.0 hubs (explained below)), and i have had no problems (of any kind) over this past week. I deliberately waited one week (before posting this solution), to see if all the problems were truly solved. And it appears that all problems have been truly solved.
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Notes:
I have used this 15 cm usb 2.0 extension cable, but i presume that other lengths will work. I just wanted to keep it as short as possible. (15 cm is roughly 6 inches, and this is usually the shortest length available.) There are many reasons for wanting to keep it as short as possible, and one of these is because i read somewhere, that it's best to try to keep the length of the usb hub's cable (from the usb hub to the computer) to a maximum length of 1 metre.
Since my mac has 4 usb ports, i presume that i could add 2 more usb hubs, as long as i also apply the same solution. I.e., my guess is that the mac can handle 4 hubs, as long as 3 of those hubs are recognised as usb 2.0.
I.e., my guess about this whole issue, is that the mac can only deal with one usb 3.0 hub.
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Confirmation test - that I can connect three usb 3.0 hubs (if this solution is used)
To test this hypothesis further (i.e., that the mac can only deal with one usb 3.0 hub), i tested the following setup:
Hub 1:
14-port anker usb 3.0 hub (with the solution of the usb 2.0 extension cable (15 cm long). I only have usb 2.0 devices plugged into this hub.
Hub 2:
10-port technet usb 3.0 hub. This usb hub is plugged directly into my mac (as normal). I have all my usb 3.0 devices plugged into it, and they run at usb 3.0 speeds.
Hub 3:
14-port anker usb 3.0 hub (with the solution of the usb 2.0 extension cable (15 cm long). I only have usb 2.0 devices plugged into this hub.
All three hubs are plugged into the mac in parallel, (i.e., none of them are daisy-chained). To be more exact, I have four usb 3.0 ports on my mac, and I have plugged the technet into the port on the far left, and the two anker hubs are plugged into the ports on the right.
Since implementing this solution (about a week ago), all of my usb devices have been working perfectly. There have been times when I have had the mac on for over 24 hours, and the usb devices still all work fine, (i mention this because before implementing this solution, there were times when the problem would get worse after 20 hours, or after many restarts).
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Exact details, and why a usb 2.0 hub is perhaps not a good solution (as compared to this solution)
I will now be a bit more specific, because sometimes that is necessary. E.g., the solution of adding a usb 2.0 extension cable, to this specific hub, does work (for me), but perhaps if i bought a usb 2.0 hub, and plugged it directly into my mac, then there might be all types of problems.
Indeed, perhaps the combination of a specific usb 3.0 hub, and this solution, does work, whereas a usb 2.0 hub might not work, because there are many usb 2.0 hubs that are using a bad/poor quality:
- chipset
- firmware
- power supply
- etc
and if any one of these is bad/poor quality, then that can cause any number of problems.
So, to be more exact about the chipset (and firmware, and power supply) of the two hubs, (that i have mentioned above), i will copy and paste the hub's title/description:
Anker AH241 USB 3.0 Aluminum 13-Port Hub + 5V 2.1A Smart Charging Port with 12V 5A Power Adapter [VIA VL812-B2 Chipset]
TeckNet HU10 USB 3.0 10 Port Hub with 48W Power Adapter and 3ft USB 3.0 Cable [VIA VL812 Chipset]
On my mac, when i check the system report (via: about this mac > system report > usb), i can see that the manufacturer and version is:
for the technet hub:
Manufacturer: VIA Labs, Inc.
Version: 90.81
for the anker hub:
Manufacturer: VIA Labs, Inc.
Version: b.e0 (Note: “Version: b.e0” , is what it shows after i add the usb 2.0 extension cable. Without this usb 2.0 extension cable, i think that it used to say “Version: b.e1”). This was true for both anker hubs.)
Before buying the anker hubs, I spoke to anker support, and they said that this anker hub uses the same firmware as their 10-port hub. (Their 10-port hub is advertised as using firmware 9081, which i'm guessing is the same as 90.81)
I have read somewhere that to avoid problematic usb 3.0 hubs, the firmware must be above 90.xx
I should add that have no affiliation with either of these two companies. The only reasons why i bought these hubs, is because i like to buy the largest hub possible (i.e., the one with the most data transfer ports), and one which has good reviews, and one which openly states what chipset they are using, and that it has a decent power supply. I also prefer hubs which only have data transfer ports, (because i don't use the charging ports, and the more things/features that the manufacturer adds to a usb hub, the more chances there are of problems occurring).
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Solutions that I tried (previously), which did not solve the five problems
Before finding this solution (of adding the 15cm usb 2.0 extension cable), i tried other ways to solve these five problems. I am listing these various attempted solutions below, because i have left these solution in place. I.e., they might (or might not) also be a part of the solution, and/or they might be of help to some people.
The things that i tried are as follows:
1 - Restart the mac.
2 - Do an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then reset the nvram.
3 - Try to plug the hubs into different ports of the mac, and then after each of these changes, do an smc reset, and then a safe boot (to let the mac do some checks and solve whatever problems), and then i reset the nvram. No matter which ports i used to plug in the usb hubs, the problems remained (especially in the long term, i.e., after a few reboots). I.e., occasionally doing these 3 resets did help, but only in the short term, (i.e., the problem resurfaced again after subsequent reboots). Many times it did not even help on that one occasion (on the first boot) after doing these 3 resets.
4 - Run “First Aid” (via disk utility) on each of the external hard drives, (including each separate volume on each external hard drive).
5 - When using any of the usb hubs, i have made sure that the ports are used in order. I did this because i did read somewhere that some people found that there were issues with usb hubs, if they left empty ports in between used ports. Ie, start by using port number 1, 2, 3, etc, and fill up the hub in that fashion. I'm not sure if this helps, but it doesn't hurt to do it like this, and there is some logic to making sure that it's done in this way.
(The first port in the hub (port number 1), is usually the port nearest to the end from which the hub's usb cable goes from the hub to the computer.)
6 - In addition to the previous point, there is also perhaps another issue, which is that it's best to keep the devices which are always active, plugged into the hub nearer to the first port (port number 1). Ie, sometimes a usb hub has many devices (and extension cables) plugged into it, but many of them are not active, and if there are too many inactive devices (or extension cables) in a row, then the devices plugged in after this, will not be active.
The reason for this, might be because the usb hub is divided into sections, (e.g., 4 ports per section), and therefore if one section is not active, then the subsequent sections are also not active. Or, perhaps it's because within one section, the first port of that section must be active, for that section to be active.
I don't know if what i've just explained (in the previous paragraph), is always true (or true at all), but i have come across issues like this myself, where after plugging in all the devices into the hub, one device is not working/recognised (but all the other devices are working/recognised), and so according to the above information, i changed the order in which i plugged the devices into the hub, and that did solve the problem (of that one device not working/recognised).
7 - I have excluded spotlight from searching each of my external hard drives.
Despite the fact that this did not solve the original five problems, i have still decided to always excluded spotlight from searching each of my external hard drives, and i now use an app called “EasyFind” to search for files/folders.
8 - I have excluded my antivirus from accessing each of my external hard drives. (This was done in the bitdefender antivirus app.)
Note: I found that to use bitdefender, i had to immediately exclude all external hard drives, because if i did not do this, then the external hard drives would not unmount, (because bitdefender was still wanting access to them, which prevents the unmount from happening). This is done in the bitdefender app, (via: preferences > exclusions).
9 - Alter the preferences in finder, (via: finder preferences > general).
10 - Relaunch finder.
11 - Run an antivirus scan (via bitdefender).
12 - Run a scan for other types of adware (via malwarebytes - anti-malware).
13 - My external hard drives (seagate backup plus desktop) came with some seagate software, but i don't install this software, (because these types of software just add problems, and aren't needed).
14 - My external hard drives are formatted in hfs+, and therefore there is nothing more i can do in respect to that. (I.e., other types of formats could be the cause of problems, for various reasons.)
15 - I have uninstalled virtualbox (in case that was causing the problem). I do not have any virtual machines running on my mac.
16 - I read somewhere something about the “usb overdrive” app, but i do not have this app on my mac (so i did not need to experiment with uninstalling it). I don't know if this would be an issue, because I use the “keyboard maestro” app, and this is always running in the background of my mac.
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Details about the problem of usb 2.0 self-powered devices not connecting to the mac
When i switched on my printer or dvd burner (which was connected via a usb cable), it would sometimes not connect to the mac. Later on i realised that the “sometimes” depended on what other self-powered usb devices were already actively being used on the mac.
The reason why this is important to mention, is because the printer and dvd burner are usb 2.0 devices, and therefore this means that this problem (of the mac having many issues, as soon as more than one usb 3.0 hub was connected to the mac), is not just about usb 3.0 devices.
I.e., this problem was not just causing issues with usb 3.0 devices (e.g., my external hard drives), but also any self-powered usb 2.0 devices (e.g., printers, dvd burners, etc). (By “self-powered”, i mean any devices that require their own power supply.)
Perhaps this means that whenever i had two usb 3.0 hubs connected to my mac (without the 15cm usb 2.0 extension cable), that then there were issues with the mac in regards to only being able to run a maximum of “x” number of active self-powered usb devices (regardless of whether they were usb 2.0 or usb 3.0 devices).
And this maximum number (“x”) included: external hard drives (which have their own power supply), printers (which were connected via usb cable), dvd burners (which were connected via usb cable, and have their own power supply), etc. And, this might also include all the usb hubs (which have their own power supply). But it (obviously) only includes the devices that were powered up.
After implementing the solution (of adding a 15cm usb 2.0 extension cable, onto two of the three usb 3.0 hubs), i seem to be able to connect as many usb 2.0 and 3.0 devices as i want, whether they're self-powered, or not. I presume that there must be some limit (to the number of devices that can be connected to the mac), but i haven't hit that limit yet (and hopefully never will).
I.e., it really seems as though the conclusion is that: As long as no more than one usb 3.0 hub is attached to the mac, then everything is fine (for all usb 2.0 and 3.0 devices).
But I'm not sure if this is also true for other usb 3.0 self-powered devices. I.e., are there similar problems as soon as more than one usb 3.0 self-powered device is attached directly to the mac? I say this because I presume that any self-powered usb device has a chipset (or whatever it's called) inside it, (just as the usb 3.0 hub does), and therefore the same problems could be caused.
And/or, perhaps this also applies to any devices that have these certain types of chipsets in them, (whether the device is self-powered, or not).
Anyhow, I've spent far too long on all of this, and so I'm not going to examine this issue any further.
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Note: Since the manufacturers (of these usb 3.0 hubs) do say that these hubs are backwards compatible with computers which have usb 2.0 ports, then this means that you can plug these usb 3.0 hubs into computers that have usb 2.0 ports. The point is, that since the manufacturers say this, this probably means that it's also safe to add a 15 cm usb 2.0 extension cable.
And this is probably more true, if you're using the original usb cable that came with the hub, or you're making sure that the cable (which runs from the usb hub to the mac) is not longer than 1 metre. However, all of this is just my take on the situation, (and I'm no expert).
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I hope this helps a few people, because otherwise I've just wasted a lot of time writing all of this...