RAID-0? D'oh!

So, as I was going through the usual logfile reports and whatnot at work this morning, I saw that my newest machine (named "catnip") had a very odd output of /proc/mdstat. I looked closer and whaddya know, I accidentally set up one of the partitions as RAID-0 when I really wanted RAID-1. RAID-0 is just striping of disks and doesn't have redundancy in case a disk fails so I had to switch over to RAID-1. Unfortunately, this is not a trivial thing. The filesystem has to be unmounted and converted, and since I didn't really have the time to mess around with boot disks, /etc/raidtab, and the various utilities, I found it quicker to just reinstall RedHat and restore from backup.

A few interesting things about installing and restoring from backup:

• RedHat's interface for setting up software RAID partitions isn't that great. I had to doublecheck everything and make sure everything was RAID-1.
• In the interest of speed, the installer will only write to the first hard disk. When you boot from the newly installed system, the RAID subsystem will "rebuild" the second disk. It took me awhile to figure out why the machine was running so slow.
• The speed of the rebuild is regulated based on disk usage. If you are copying files around, the rate will drop to 3 Megs a second or less. If you cease disk activity, the rate will slowly be increased until it maxes out. (similar to TCP window size)
• When restoring from backups, be careful with files like /etc/fstab and /etc/raidtab. I accidentally put the ones in from my last backup, which differed from the current installation. Fortunately the system was smart enough to realize that you can't use an already mounted partition as swap space. But I could have easily torched a partition that way.

Total time to re-install and restore my data was 98 minutes. And nothing was lost. Not too shabby.