Disksuite: Mirroring on a 2 disk system
2007-12-24 20:31:00
We are primarily a DEC shop, but recently bought a 220R server. The machine
came with 2x 36GB drives, and our general design called for all user files
to be stored on another machine, that's a lot more disk than I need for
system stuff. I delved into DiskSuite to see if I could use one disk as a
mirror of the other for increased system reliability.
I managed to successfully mirror /, /usr, /var, swap, and an AFS cache, and
put 3 database replicas on an unused partition on each disk (6 copies of
database total). I was rather pleased to see that system stayed up normally
when simulated failure of a drive. However, I was displeased to learn that
the system would not reboot with one drive missing --- according to metadb
man page
"the system will not reboot without one more than half the total replicas"
Am I missing something, or does this mean that there is no effective way
to obtain of fault-tolerant mirroring on a 2 disk system? Is there a way
to instruct the system to reboot if exactly half the replicas (e.g. one disk)
are not available?
Or should I just revert to simpler plan of no mirroring and periodically
copy contents of system disk to spare? System would not stay up upon failure
of system disk, but a quick reboot and swapping of disks should get me back
up.
Thanks in advance for your assistance. A summary of responses will be posted.
Tom Payerle
Dept of Physics payerle at physics.umd.edu
University of Maryland (301) 405-6973
College Park, MD 20742-4111 Fax: (301) 314-9525
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