From: Urie, Todd (TUrie@trueposition.com)
Date: Tue Jun 04 2002 - 09:20:55 EDT
I am configuring a SunFire280R to use disk mirroring using DiskSuite. The
280R has only 2 internal disks, which raises a question regarding metadevice
databases.
Since DiskSuite requires that there be at least 1/2 the number of db's + 1
in order to boot a system, it is impossible to set a practical metadb
configuration such that, in the event of a complete failure of one of the
disks, the system can be rebooted. Therefore, by configuring mirroring on a
280R (or any other 2 disk system), I only gain the ability to keep my system
up in the event of a complete failure of 1 of the disks. Not suggesting
that 'only keeping the system up' is bad, just trying to explicitly
understand the limitations and risks that are not addressed.
Also, if I restrict all of my metadb's to a single disk slice on each disk,
then I am at risk for problems on that slice. If I place my metadb's across
2 or more slices on each disk, then I can still boot a failed system in the
event of a partial disk failure (e.g. enough slices remain to satisfy the
1/2 + 1 requirement).
My questions are: How often do you actually see a failure that is
restricted to a slice or 2? Are there any flaws in my logic above? Are
there any undesirable effects that result from having metadb's on slices
that contain filesystems?
I'll summarize.
Thanks,
Todd Urie
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