Time Machine and USB 2.0 Observations

[srichart1]

I wanted to share some of my findings about USB 2.0 and Time Machine on my IMac. I have a USB Port Expander made by Belkin and had a USB 500gb hard drive going through the expander. I began to notice how poorly time machine was running and how it would keep the hard drive writing all of the time. At the same time I noticed that my IPOD and IPHONE, also connected through the USB expander, was taking forever to update and sometimes failing. I did some testing and found that the USB 2.0 hard drive works best plugged directly in back of the IMac. If you use it through an expander it WILL not work as well.
The port expander make/brand does not seem to matter much, as discovered upon further testing.

Time Machine is ok, but I am not impressed as much as I would like to be. It takes too much storage space and I can't really see any compression schemes in use, which would be very helpful. I am not sure if it is really doing an incremental backup either.

Conclusion. I would recommend anyone who uses time machine to get a hard drive that is at least 2x the size of the one they are backing up and to get Firewire 400/800. USB 2.0 does work, but is not as reliable as FW and is very picky when sharing the bus with other devices.

I hope this helps someone. Thanks.

 

[CBAviator]

I use Firewire 400 and Time Machine works like a charm!

 

[Yuppi]

The reason might be as simple as some power problems. When you have a passive hub, means it has no own power supply, the disk/ipod whatever share their power source. Which might be the single USB-Port which can only deliver some amount of energy. The harddrive might thus be underpowered causing poor performance. If the harddrive or the usb expander has it's own power supply, just ignore this idea
But one thing is always true. If an expander is used the time a signal travels is longer which might have a very very small impact on the performance of random accesses.
My Disk is connected trough the ACD and works perfectly.

 

[srichart1]

Expnder

The reason might be as simple as some power problems. When you have a passive hub, means it has no own power supply, the disk/ipod whatever share their power source. Which might be the single USB-Port which can only deliver some amount of energy. The harddrive might thus be underpowered causing poor performance. If the harddrive or the usb expander has it's own power supply, just ignore this idea
But one thing is always true. If an expander is used the time a signal travels is longer which might have a very very small impact on the performance of random accesses.
My Disk is connected trough the ACD and works perfectly.

Mine is powered, and I agree with what you said about the potential of the bus being underpowered. Thanks.

 

[deathshrub]

Expander?

 

[ADent]

Expander = USB Hub

I haven't had any problems with Time Machine or my iPod on my mini - but I have everything plugged directly into the 4 USB ports (except the mouse, which is plugged into the keyboard).

Time Machine uses no compression, so it is fairly useless on a drive the same size as the original. I have 64.56GB used on my machine, and my Time Machine drive is using 63.12GB. I turned it on on Saturday and haven't done anything with big files (I assume TM becomes a space hog when editing video).

It does incremental backups.

Are you sure it is not Spotlight causing the disk to run?

I agree FireWire is a better choice for Macs in most cases - it is just getting hard to find reasonably priced.

 

[MikeTheC]

One of the biggest -- if indeed not the biggest -- problems with USB is that the bandwidth is SHARED, not dedicated. Therefore, the more devices you plug in, the further that bandwidth gets spread across 'em.

Also, USB2 has a PEEK throughput -- basically a "burst" mode, if you like -- of 480MBps, but typically is nowhere near that high.

Firewire uses dedicated bandwidth for all attached devices, and is designed to run flat out at 400MBps, consequentially having a more stable and higher sustained throughput.

In a competition, there's simply no comparison between USB2 and FireWire. Period, end of statement.

 

[srichart1]

USB = Slower than FW

One of the biggest -- if indeed not the biggest -- problems with USB is that the bandwidth is SHARED, not dedicated. Therefore, the more devices you plug in, the further that bandwidth gets spread across 'em.

Also, USB2 has a PEEK throughput -- basically a "burst" mode, if you like -- of 480MBps, but typically is nowhere near that high.

Firewire uses dedicated bandwidth for all attached devices, and is designed to run flat out at 400MBps, consequentially having a more stable and higher sustained throughput.

In a competition, there's simply no comparison between USB2 and FireWire. Period, end of statement.

I couldn't agree with you more on USB being inferior to Firewire. I do have my USB 2.0 HD running pretty good the way it is currently connected and it doesn't run all the time as before. The only problem I now have is that once in a while, when coming out of a sleep, the Time Machine drive (USB 2.0) disappears and will not reappear without unplugging the drive or rebooting.

It is strange..

 

[srichart1]

Time Machine

Expander = USB Hub

I haven't had any problems with Time Machine or my iPod on my mini - but I have everything plugged directly into the 4 USB ports (except the mouse, which is plugged into the keyboard).

Time Machine uses no compression, so it is fairly useless on a drive the same size as the original. I have 64.56GB used on my machine, and my Time Machine drive is using 63.12GB. I turned it on on Saturday and haven't done anything with big files (I assume TM becomes a space hog when editing video).

It does incremental backups.

Are you sure it is not Spotlight causing the disk to run?

I agree FireWire is a better choice for Macs in most cases - it is just getting hard to find reasonably priced.

Yes, Time Machine is almost like a 'backup for dummies'. No offense to anyone, but it is a no brains backup module for the masses. Unfortunately, with no adjustable compression settings or any other settings to make it tunable, it is just really more of a novelty. But, that being said, I am using it on my machine so it is of some value.