My Fusion Drive Got Slow, How I Fixed It

[DerekS]

My speeds were getting terrible (Dec 2012 model, factory 1TB Fusion.)

I was seeing < 100MB/sec in both directions.

I rebooted to single user mode (command-S during boot) and at the prompt entered:

fsck -ffy

One of the messages that scrolled by was "trimming unused blocks."

After the reboot, my speeds were back to factory fresh!

202MB/sec write, 352MB/sec read

Just wanted to share this tip if others feel like their Fusion drive is starting to suck! My guess is that OSX fails to trim the SSD on its own.

 

[Brian33]

Very interesting! Have you checked to see if OS X reports trim enabled in the System Information utility for that drive? (Hardware-->SATA, under the SSD info look for "TRIM Support: Yes")?

Also, are the two "f" characters on your fsck command a typo? Looking at the man page it seems a single "f" option is sufficient. (There's also a scary warning about the "y" option!)

Thanks for the info, I'll keep it filed away. That's a big performance increase.

 

[Weaselboy]

Very interesting! Have you checked to see if OS X reports trim enabled in the System Information utility for that drive? (Hardware-->SATA, under the SSD info look for "TRIM Support: Yes")?

Also, are the two "f" characters on your fsck command a typo? Looking at the man page it seems a single "f" option is sufficient. (There's also a scary warning about the "y" option!)

Thanks for the info, I'll keep it filed away. That's a big performance increase.

He has a factory Fusion drive, so TRIM would be enabled. And you are correct "fsck -fy" will do the trick.

 

[sjinsjca]

My speeds were getting terrible (Dec 2012 model, factory 1TB Fusion.)

I was seeing < 100MB/sec in both directions.

I rebooted to single user mode (command-S during boot) and at the prompt entered:

fsck -ffy

One of the messages that scrolled by was "trimming unused blocks."

After the reboot, my speeds were back to factory fresh!

202MB/sec write, 352MB/sec read

Just wanted to share this tip if others feel like their Fusion drive is starting to suck! My guess is that OSX fails to trim the SSD on its own.

Interesting. I doubt the trimming is the reason, though.

It's not a bad idea to occasionally boot into the recovery partition (hold cmd-R down during boot) and run Disk Utility's repair and permissions-repair functions. This would be safer than futzing around in Terminal.

 

[DerekS]

Yes, factory SSD (factory Fusion, really) and TRIM does show enabled.

I am convinced that trimming made the speed improvement, as I had already run repair permissions and such in Disk Utility many times prior.

My conclusion is that OSX does not automatically trim Fusion drives.

 

[rbart]

I have tried many times to make my DIY Fusion drive work on my iMac (Lacie TB SSD + internal hard drive).
It works after a fresh install with good write perf, but after few days, write perfs are getting bad (50Mb/s with blackmagic).
I suspect something with TRIM (it's supposed to be active on my Mac) but ...

 

[andycho7]

I have tried many times to make my DIY Fusion drive work on my iMac (Lacie TB SSD + internal hard drive).
It works after a fresh install with good write perf, but after few days, write perfs are getting bad (50Mb/s with blackmagic).
I suspect something with TRIM (it's supposed to be active on my Mac) but ...

Did you manually enable the TRIM? I did a DIY fusion drive on my 2011 iMac 27 inch with 250GB Samsung Evo. Right after the OS installation, I checked the system report and TRIM wasn't enabled by default.

 

[shaunp]

Yes, factory SSD (factory Fusion, really) and TRIM does show enabled.

I am convinced that trimming made the speed improvement, as I had already run repair permissions and such in Disk Utility many times prior.

My conclusion is that OSX does not automatically trim Fusion drives.

Perhaps raise it as a bug with Apple?

 

[rbart]

Did you manually enable the TRIM? I did a DIY fusion drive on my 2011 iMac 27 inch with 250GB Samsung Evo. Right after the OS installation, I checked the system report and TRIM wasn't enabled by default.

Yes, it's enabled with Trim enabler.