My Fusion Drive Got Slow, How I Fixed It

DerekS

macrumors 6502
Original poster
Jun 25, 2007
338
3
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

macrumors 6502a
Apr 30, 2008
818
68
USA (Virginia)
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

Moderator
Staff member
Jan 23, 2005
30,255
9,974
California
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

macrumors 68020
Oct 30, 2008
2,179
505
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

macrumors 6502
Original poster
Jun 25, 2007
338
3
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

macrumors 6502a
Nov 3, 2013
518
233
France
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

macrumors member
Dec 2, 2013
74
2
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

macrumors 68000
Nov 5, 2010
1,811
1,393
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

macrumors 6502a
Nov 3, 2013
518
233
France
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.
 
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