I periodically repair my main start up drive by running Single User Mode. The drive (two SSDs in a RAID 0 configuration) has been working fine. But the last two times I've run Single User Mode, after "Checking extended attributes file" there is a long pause, then "Failed to issue COM RESET successfully after 3 attempts. FAILING..." A hard shut down is required.

A quick Google suggests hard drive failure, but it seems to be working fine. If I boot from a clone on another drive and run Repair Disk on the drive in question, it passes.

All my software is up-to-date (10.6.8). I've run DiskWarrior. I recently ran TechToolPro to optimise the drive, which is less than half full.

I am working on the drive in question as I type, but am backing up daily...

Any ideas? Thanks.

Since my last post, I have reset the PRAM. /sbin/fsck -fy still gets the same FAILING... message.

I have the startup drive (SSD) and 2 clones on 2 other normal spinning hard drives. I have tried to run single user mode /fsck on each of the drives and come up with the same FAILING message.

I am able to successfully run Repair Disk from Disk Utility on each of the drives. Each of the drives boots properly.

I'll now try just unplugging the computer for awhile, then see if I can find the Hardware Test DVD...

I ran the extended Apple Hardware Test: "No problems found"

I unplugged the power cord to reset the SMC(?). No good.
I tried to boot in Safe Mode, but everything froze when the progress bar was about a third of the way across.
I ran the 10.6.8 Combo Updater. No good.
I made my mind up to call Apple tomorrow, since this thing is still under warranty.

I finally ran OnyX, the Automation selection. On reboot, I reset the PRAM. On reboot, I started in Single User Mode. I'll be damned if the thing didn't run the course and pronounce everything okay. I rebooted into Safe Mode successfully.

I can report that everything seems back to normal now.

I guess I owe my good fortune to OnyX and perseverance. Must have been some system cache that needed emptying?

There are some circuits deep down in the hardware that may not be reset by a restart. Only a complete shut down and restart will clear them. Although I cannot prove it, I think that accounts for a number of otherwise inexplicable miracle "healings".

There is system software code in RAM that is not replaced by a restart. It is cached, to make the restart faster. Clearly, if any of that code is corrupted in RAM, a shutdown, a pause to let the contents of RAM be lost, and a reboot are needed.

Before you posted the Onyx/restart 'fix' I was wondering to what extent your RAID setup and the use of TTP's disk optimization routine could have been involved in generating the error message you got, especially if the problem started after the optimization.

I would think that defragging an SSD isn't exactly 'good' for its longevity, but more importantly, it may actually make things worse for RAID volumes since the TRIM command isn't supported if the drives are part of a RAID volume.

You may want to consider running your Single User Mode repair routine both before and after the next TTP optimization and see if the problem recurs. Still, even if you can duplicate the issue AND fix it the way you did last time, it's not immediately clear what the underlying problem is.

This whole SSD/RAID arrangement is a bit of an experiment for me. It is quick. The trade-off is longevity, which is one of the reasons I keep two clones on the go with daily backups. (It only takes a couple minutes with Carbon Copy Cloner.)

I did wonder about TTP optimizing across two separate drives and I will take your advice next time (and if) I continue to run the optimizing routine.

Anyway, this crisis seems to have passed...

twin SSDs eh? don't see that very often.

I read this article:
Icy Dock review
detailing how you could put 2 x 2.5" hard drives in a 3.5" raid enclosure, then slot that into the extra optical drive bay in a new MacPro. I was intrigued.

I started with a couple 250Gb WD drives. Then, I read about the Intel 320 series SSD's and their 5-year warranty. Thought I'd give it a try with a couple 80Gb SSD's – just installing the OS and applications.

Sometimes, I wait impatiently for something to launch or save, then realise it happened so quick, I missed it. I don't know about 10 times faster than standard drives, but certainly everything is noticeably quicker.

One of the old WD drives is now in my MacBook, the other is waiting for an external case.