Normal behavior or failing HDD?

[smirk]

Hey everyone,

I have a late-2015 iMac 27" with the stock 2TB fusion drive, running Mojave and formatted as APFS. I feel like it has been slowing down lately in ways that seem new, but nothing drastic that screams "drive failure!"

When the computer was new, things involving drive access seemed pretty speedy, even after it was loaded with 1.5TB of data from the previous iMac. But now, it seems less so. Apps take 3-4 bounces to launch, where a couple years ago I'm pretty sure they took 1-2 bounces. Where it's most pronounced is when a VMWare Fusion guest OS is doing something drive intensive, like starting up, updating its OS, or indexing the drive. When this happens, the host OS becomes much more unresponsive than it used to. Again, nothing so bad that it's clearly a failing drive, but enough that I'm digging into it and writing this post.

I've run fsck, run drive self tests, and looked at SMART data, but nothing bad has shown up.

Yesterday everything screeched to a halt and macOS said it couldn't launch an app because it was out of storage. The Finder was unresponsive, and Terminal.app wouldn't even launch so I could examine free space, so I had to physically shut the computer off and boot into single-user mode. `df -H` showed 22GB free. I ended up deleting some unneeded files to free up more space, and it booted up normally after that. Doing a disk repair in Disk Utility showed no issues.

I was wondering if anyone had any thoughts or insight on this. It's natural for things to slow down over the years as newer versions of the OS are installed, and I suppose the disk could have actually filled up with some temp files that were then purged when I rebooted. On the other hand, I'm wondering if the 2TB Seagate that makes up the bulk of the fusion drive is on its way out and the SMART data simply doesn't reflect it yet.

Thanks!

 

[Juicy Box]

I am not sure if your problem is with the Fusion Drive, but I had a failed Fusion Drive in my Late 2012 iMac.

I got the top of the line iMac with the 1TB Fusion Drive, and some where about 1.5 years in, I started seeing subtle issues with it.

Most times, a restart would correct the issue, and I would tend to go months without restarting so it is hard to tell when the Fusion Drive issues actually started.

About 2 years in, I had issues waking from sleep, unresponsiveness, and eventually boot issues. Sometimes would take multiple attempts to reboot. The folder with the "X" or "?" (can't remember what the symbol looks like) would be there on start up sometimes, only for a few seconds, then longer, and longer. Sometimes almost boot, but hang half way there.

There was other strange glitches, it was if there was pieces missing from the OS. For example, when dropping down "file" on the menu bar, some things that should be there would be missing.

Wiping the drive and re-installing from a back up would work for only so long before the issues came back.

I have Apple Care, so around 2.25 years in, I called Apple support. Gave all my symptoms and they agreed with me that it sounded like a failed drive, maybe one with bad sectors. They set me up with an Apple Store appointment, which is not exactly local for me.

I took my iMac to the Apple Store, only for them to wipe the drive and have it pass the hardware diagnostic test. They would blame the software, saying it was corrupt, and send me home.

The problem came back a few months later, then called Apple Support, then the Apple Store Appointment, then the same thing happened. Then I was sent home.

It happened again a few weeks later, and the same thing happened again. I asked them if maybe there are bad sectors on the drive, and each time they wipe the drive, the diagnostic test isn't picking up the bad sectors, and they said even if it was true, they couldn't replace the drive unless it failed their test.

They kept it for 2 weeks, doing an extended test, which it passed. So, I was sent home with it again.

A few days later, it totally failed, and I couldn't boot at all. Not even an external drive, internet recovery, or anything.

I called again, took it to the store, and they couldn't get it to boot for 2 hours, until they were able to boot into their diagnostic OS. It finally failed the test right away, and I got a new drive installed.

On the other hand, I'm wondering if the 2TB Seagate that makes up the bulk of the fusion drive is on its way out and the SMART data simply doesn't reflect it yet.

My SMART data never showed issues with I was having obvious drive issues.

 

[komatsu]

@smirk can you run this on your disk:

https://www.volitans-software.com/apps/smart-utility/

 

[smirk]

@smirk can you run this on your disk:
https://www.volitans-software.com/apps/smart-utility/

That's actually what I used when I originally checked the SMART data. Although now that I'm looking more closely at it, I see that the SSD portion of the fusion drive had 3 CRC errors. Not sure if that's significant or not.

 

[HDFan]

I have a late-2015 iMac 27" with the stock 2TB fusion drive, running Mojave and formatted as APFS. I feel like it has been slowing down lately in ways that seem new, but nothing drastic that screams "drive failure!"

When the computer was new, things involving drive access seemed pretty speedy, even after it was loaded with 1.5TB of data from the previous iMac.

`df -H` showed 22GB free. I ended up deleting some unneeded files to free up more space, and it booted up normally after that.

You need a bigger drive or need to clear out a lot more space. The 20% threshold for a 2 TB drive is 1.6 TB. Using more than that can cause problems.

 

[Fishrrman]

"Yesterday everything screeched to a halt and macOS said it couldn't launch an app because it was out of storage."

Sounds to me like your drive may be "fuller than you think it is".

Here's what to do (quick, easy, costs nothing):
Download DiskWave from here:
https://diskwave.barthe.ph
It's small in size and free.

Open DiskWave and go to the preferences.
Put a checkmark in "show invisible files".
Close preferences.

The DiskWave window shows you all your drives in plain English (no ridiculous graphical formats).

Now you can "click around" and see what's consuming your space.
It might be invisible temp files, or perhaps TM "snapshots" (or whatever they're called, I don't use TM)?

ONE OTHER THOUGHT:
If you want to really speed up the overall performance of the iMac, even with a nearly-full fusion drive, you could do this:
1. Buy an EXTERNAL USB3 SSD
2. Plug it in and set it up to be your regular boot drive (with applications, and "basic" accounts -- leave large libraries of stuff, movies, music, pics, on the fusion drive)
3. Boot that way.
Keep the SSD "lean and clean", and the iMac will boot quickly and run consistently faster.

 

[mikehalloran]

I feel like it has been slowing down lately in ways that seem new, but nothing drastic that screams "drive failure!"

Disk too full as others have mentioned.

ONE OTHER THOUGHT:
If you want to really speed up the overall performance of the iMac, even with a nearly-full fusion drive, you could do this:
1. Buy an EXTERNAL USB3 SSD
2. Plug it in and set it up to be your regular boot drive (with applications, and "basic" accounts -- leave large libraries of stuff, movies, music, pics, on the fusion drive)
3. Boot that way.
Keep the SSD "lean and clean", and the iMac will boot quickly and run consistently faster.

Good suggestion to get a T5. Bad suggestion to make it your boot drive. A T5 is USB 3/3.1 (how you connect doesn't matter since the drive inside is slower than USB 3). That's as fast as it can go which is a lot slower (1/3 the speed) than a fusion drive with a lot of space. A T5 or any USB 3 SSD is 4.9x faster than the HHD portion of the fusion drive according to Samsung.

How to use it as an external:

In Mavericks and iTunes 12.7, it's easy to offload your iTunes and Photos libraries to an external without creating Symbolic Links in Terminal—or create SymLinks in earlier OS. Tons of support articles on how to do this. Also offload any movies—they'll run just as fast.

If you want an external that boots as fast (or faster) as your 2015 when new, get the Samsung X5 plus the Apple TB2 to TB3 adapter.

Dirty little secret: the 2015 iMac used an NVMe 2 blade that's half the speed of the PCIe 3 x4 bus. An X5 over Thunderbolt 2 is as fast as the PCIe bus inside your 2015 and 6x the speed of a T5.

Now you can use your internal storage as just that remembering that you have an HDD in there that's really, really slow by comparison.

If you do get an X5, when booted from it, run the following command in Terminal to enable TRIM: sudo trimforce enable
TRIM is not supported over USB-anything so, while you can run the command booted from a T5, it will not be enabled.

 

[smirk]

Hey, thanks for all the help and info, everyone.

I cleared off some room on the drive. Do you think it will be better now, or should I back it up, wipe the fusion drive, and copy everything back, to sort of redistribute everything? My thinking is that for a long time now the drive has been "too full" for the file system to breathe, so files could have gotten packed together inefficiently. I'm totally speculating on this without any knowledge of how APFS works, so maybe that makes no sense.

Thanks!

 

[mikehalloran]

Wiping and redistributing or whatever you think will happen... won’t. The OS makes those decisions in a fusion drive based on your usage and you have no way of controlling it.

If the performance is acceptable, leave it alone. If it’s not fine, the cure is to put a 2TB SSD in there. The fastest will be to replace the NVMe 2 blade in there with a fast 2TB NVMe 3 x4 blade to take advantage of the bus speed. NVMe blades are not created equal. The 970 EVO and Aura X2 Pro are fast enough to make a big difference.

 

[smirk]

Thanks Mike, I appreciate your comments. I'm sure what I was thinking was flawed, but I was actually thinking about the data packed into the HDD, not the SSD. As in maybe related files are scattered all over the HDD due to it being so full when they were originally written. I'm sure I'm overthinking it.

 

[HDFan]

As in maybe related files are scattered all over the HDD due to it being so full when they were originally written. I'm sure I'm overthinking it.

I have seen posts saying that MacOS doesn't need hard disk directory optimisation and others saying that it does. There are utilities, such as DiskWarrior, that will analyse your disk and then optimise the directories:

 

[mikehalloran]

DiskWarrior became obsolete over a decade ago with the introduction of Mac OS 10.5. It doesn't actually fix anything — it can't. All tests deliberately install a corrupt directory that DW magically "fixes". The preference and other files that could cause problems according to their marketing dept., can't cause you problems. Really.

I've had it for many years now. When DW shows a lot of problems, it's time to replace the drive. Seriously, that's all it's good for but I look at a lot of problem drives so I keep an active license.
[doublepost=1559456630][/doublepost]

As in maybe related files are scattered all over the HDD due to it being so full when they were originally written. I'm sure I'm overthinking it.

Interestingly, Alsoft, the makers of DiskWarrior, used to make an excellent optimization app and I had it. Had to stop using it around OS 8 because it no longer worked. When I asked them, they told me that Apple had stated disk optimization was never necessary. Then went on to say that Apple was right and Alsoft could prove it.

 

[HDFan]

Alsoft, the makers of DiskWarrior, used to make an excellent optimization app and I had it. Had to stop using it around OS 8 because it no longer worked.

Techtool Pro has it. Optimisation certainly can be useful as it reduces block seek times, particularly for large files. But MacOS already has built-in optimisation so it's normally not needed.

https://www.macworld.co.uk/how-to/mac/defrag-3600241/

But running a full optimisation does make a difference:

 

[mikehalloran]

Techtool Pro has it. Optimisation certainly can be useful as it reduces block seek times, particularly for large files...

Quite familiar with that graphic. I love TTP screen shots.

Ok, I get that you don't believe this but no it can't. Really and truly.

I know. It looks nice and you feel good doing it but it does not improve the performance on a Mac. I've had hundreds of them to play with and you can bet that I ran before and after performance tests over the years to see if disk optimization made any difference. 500GB file transfers, huge streaming audio and video, DAW bounce to disk... None. Zip. Zero. Zed.

I maintain my license for TechTool Pro. Unlike when version 1 allowed me to recover most of the data on the original SCSI drive attached to my Mac Plus, TTP can't fix anything anymore. It is still a great diagnostic tool and that's why it's worth every cent to me. Just last night, I used it to find a stick of faulty RAM and an SSD in the early stages of failure on a 2010 iMac. Emailed screen shots to Crucial and OWC—RMAs are in and the defective parts have been shipped for warranty exchange.

 

[smirk]

@mikehalloran why do you say that TTP and Disk Warrior can't fix anything anymore?

I've used defragmenters/optimizers for a long time (not in recent years, though) and my observation, for what it's worth, is that it makes a decent performance difference on older, slow drives, but not as much on newer, faster ones. That's anecdotal, though, I don't have any benchmarks to back it up other than counting icon bounces in the dock.

 

[HDFan]

Techtool Pro has it. Optimisation certainly can be useful as it reduces block seek times, particularly for large files. But MacOS already has built-in optimisation so it's normally not needed.

The reason for my screenshots was to show that although MacOS already has build-in optimisation (so optimisation is not generally needed) it isn't perfect. The screen shot was to allow a comparison of the automatic optimisation done by MacOS with that done by TechTool Pro. Given that there wasn't that much difference (as shown by the graphics), the cost is rather high. Even for a small disk it takes hours, and obviously causes a lot of additional wear and tear on the disk.