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14 December 2004

Nerd Factor X




I really like UNIX sometimes. My home FreeBSD box has a dying hard drive. It started reporting ominous READ_DMA log entries in the daily emails it sends me (what, your operating system doesn't send you email?). I stupidly ignored these, and a few days later found that it wasn't booting. Attach a monitor to it, I see that it has detected disk errors and helpfully dropped into single-user mode for me to fix.

This is very handy, as I could simply comment out the relevant entry in the /etc/fstab file, and continue to boot. Because the failing drive was mounted on /home, I ended up with a box that didn't have this directory, but was otherwise perfectly fine!. Crisis averted. Box continues to function. I get to continue to attempt to resurrect it at my leisure.

The problem was that the dying drive wasn't responding to fsck -y, which is the disk repair tool. So I'm casting around for ideas and find a helpful suggestion on a mailing list to just mount the failing drive read-only. This lets you salvage anything useful without requiring the disk to be in a perfectly consistent state. Hooray for UNIX!

As it turned out there was only a few files of only minor importance (err, actually just the subversion repository!), but it was nice to get them back.

A few months back I bought a couple of 250GB SATA drives and Promise RAID controller. I had for a while been running these babies in the FreeBSD box and had been slowly (too slowly as it turned out) migrating data from /home to the new mirrored drive array. Guess that will have to happen sooner rather than later.

So there you have it, a fairly happy ending to a disk crash story. Maybe after all these years I'm finally learning something.