[jacix]

I set up a Fusion drive on my 2011 MBP with a 1TB Seagate HDD in the standard drive bay and an OCZ 256GB SSD where the superdrive used to be. It was blazingly fast for a while but has gradually slowed down. I did some testing dd'ing files into /dev/null while watching iostat and found that new data goes to the HDD while old files live on the SSD. My Fusion drive is working backwards! How does Fusion know which is the SSD and how can I correct it? I did the initial setup with both drives in a dual-port USB/SATA dock then used Carbon Copy Cloner to copy my original HDD to the Fusion before testing and installing it. System Information properly reports the OCZ (/dev/disk0) as solid state so I'm stumped.

Any ideas? Thanks!

[blaineoh]

Everything seemed to go as planned, though my computer wouldn't initially boot correctly after the first attempted install of 10.8.3. Now it's incredibly fast... BUT! A large amount of applications crash upon opening. Large Pro apps seem to do well. Final Cut opens correctly in about 4 seconds. But GarageBand, iPhoto, MainStage and others abort immediately. Specifically, this seems to be the problem

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '

Application Specific Backtrace 1:
0 CoreFoundation 0x98832e9b __raiseError + 219

If this is causing this amount of headaches now, I think I'll try the Home folder on the HDD version instead. Maybe I was asking too much?

[monstasaurous]

jacix, on 20 March 2013 - 08:53 PM, said:

I set up a Fusion drive on my 2011 MBP with a 1TB Seagate HDD in the standard drive bay and an OCZ 256GB SSD where the superdrive used to be. It was blazingly fast for a while but has gradually slowed down. I did some testing dd'ing files into /dev/null while watching iostat and found that new data goes to the HDD while old files live on the SSD. My Fusion drive is working backwards! How does Fusion know which is the SSD and how can I correct it? I did the initial setup with both drives in a dual-port USB/SATA dock then used Carbon Copy Cloner to copy my original HDD to the Fusion before testing and installing it. System Information properly reports the OCZ (/dev/disk0) as solid state so I'm stumped.

Any ideas? Thanks!

That's definitely a strange situation, especially since it was working fine and as expected for a while.

I'm not entirely sure exactly how OS X knows which drive is the SSD, I'm assuming it can determine it just like the System Information can. Another thought is that it may do a read/write speed test to determine which drive is the faster one, that way if you made a fusion drive out of two HDD's with one at 5400rpm and the other at 7400rpm it would know to write to the faster one first. But that's all just speculation.

I haven't experienced any strange behavior when making the fusion drive externally and then moving it internal, however it's hard to tell exactly what's going on under the hood. My guess is that it's filling up the SSD, and as you gradually start to use the computer more it'll get a better idea of what files you use more frequently and slowly shuttle them over to the SSD. A lot of this depends on how you use your computer, so results are gonna vary.

What was your setup like prior to the fusion drive? Did you use the OCZ for your system and the HDD for media?

[monstasaurous]

blaineoh, on 03 April 2013 - 05:18 AM, said:

Everything seemed to go as planned, though my computer wouldn't initially boot correctly after the first attempted install of 10.8.3. Now it's incredibly fast... BUT! A large amount of applications crash upon opening. Large Pro apps seem to do well. Final Cut opens correctly in about 4 seconds. But GarageBand, iPhoto, MainStage and others abort immediately. Specifically, this seems to be the problem

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '

Application Specific Backtrace 1:
0 CoreFoundation 0x98832e9b __raiseError + 219

If this is causing this amount of headaches now, I think I'll try the Home folder on the HDD version instead. Maybe I was asking too much?

That's strange behavior to be sure, but unless you install all of your applications locally (in your ~/Applications/ folder rather than /Applications) I'm not sure how it would help.

It may be worth trying to reinstall those applications. Did you migrate from a previous install after setting up the fusion drive?

[MasonS]

This how-to does not actually help you to create a true fusion drive. What you are actually doing is creating one volume group out of the SSD and the harddrive and presenting that to the OS as one or more logical volumes. This is a very different sort of beast than a fusion drive.

With this setup, If the SSD is the first drive in the volume group, new files will be written to the SSD until it fills up and then files will be written to the harddrive. This explains why one commenter witnessed, using iostat, new files being written to the harddrive rather than the SSD and others said it started off fast and then got slower later on.

If you don't want to buy a fusion drive, but do want fast boot times and fast loading of programs, I would suggest using these as two independent formatted drives. Install the OS and programs on the SSD and store the majority of your files on the harddrive. If you are working with a particular file and want it to load quickly, move it to the SSD while you're working on it and then later move it to the harddrive for long term storage. Yes this is manual process and not as slick as the optimization provided by a real fusion drive, but it will allow you to have much more data on the fast SSD than is possible with a fusion drive.

In my case, I have a single SSD in my computer and I store all of my data on a network file server. The computer boots and loads programs very quickly, wakes from sleep in an instant and is totally silent. The file server provides massive storage capacity for my files and allows me a destination for my time machine backups. When I'm working on a file that needs the speed of the local SSD, I just copy it to my computer and copy it back to the file server when I'm done.

[jstewart]

I have a 240 GB SSD drive and a 500 GB HDD (this one mounted in the optical bay). When I used the coreStorage create command, I get "Error: _69888: Couldn't unmount disk" and can't go any further. I've tried this booted off an external hard drive as well as booting off of the recovery disk as well. I'm running 10.8.3. Would appreciate any help.

[mutatio]

I'm not sure if anyone else has run into this, though I have heard about people inadvertently creating a Fusion drive when an SSD is newly installed and the Disk Utility is run. I ran into somewhat of a similar process. I upgraded my Mac Mini to a dual drive system with an SSD. I put the SSD in the primary drive position and moved the HDD to the secondary slot.

After installation of OS X I made the mistake of running the "diskutil cs create drivename driveIDs" script in terminal within OS X, thinking that it would work (I hadn't read ahead in the guide and saw only initially took note of the mention of terminal being run from the Apps folder). The command aborted and said it could not complete. When I rebooted in the recovery HD the disks showed up as red in disk utility and a cue popped up saying that the drives needed to be fixed. I took a chance on the "fix" and Disk Utility then engaged in what appeared to be all of the steps laid out here for manual execution. The install on the SSD was erased, per the prompt that had come up but I went ahead and did a fresh install on the newly "fixed" Fusion drive and have been up and running ever since. :-)

[monstasaurous]

mutatio, on 04 May 2013 - 05:15 PM, said:

I'm not sure if anyone else has run into this, though I have heard about people inadvertently creating a Fusion drive when an SSD is newly installed and the Disk Utility is run. I ran into somewhat of a similar process. I upgraded my Mac Mini to a dual drive system with an SSD. I put the SSD in the primary drive position and moved the HDD to the secondary slot.

After installation of OS X I made the mistake of running the "diskutil cs create drivename driveIDs" script in terminal within OS X, thinking that it would work (I hadn't read ahead in the guide and saw only initially took note of the mention of terminal being run from the Apps folder). The command aborted and said it could not complete. When I rebooted in the recovery HD the disks showed up as red in disk utility and a cue popped up saying that the drives needed to be fixed. I took a chance on the "fix" and Disk Utility then engaged in what appeared to be all of the steps laid out here for manual execution. The install on the SSD was erased, per the prompt that had come up but I went ahead and did a fresh install on the newly "fixed" Fusion drive and have been up and running ever since. :-)

Haha at least it turned out O.K. for you!

I've definitely seen this happen, and Disk Utility certainly does know how to make a fusion drive. However the option just isn't currently there on the surface.

I believe that feature is there in case something goes awry, you'll be able to fix the fusion drive setup that came with your machine initially.