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Questions and Answers
Amy Rich
Q: I recently had one of my machines panic and spit out the following
message. I have the root disk mirrored with DiskSuite, which I assume has something
to do with the md output:
savecore: [ID 570001 auth.error] reboot after panic: \
md: state database problem
A: The md: state database problem message probably indicates that something happened to one of the mirrors, and there weren’t enough remaining metadevice database instances to reach a majority consensus. The majority consensus algorithm is used because there is an inherent problem determining which metadevice state database instances have reliable data in them. With a majority consensus, a majority of the database replicas must agree with each other before any of them are declared valid. This requires creating at least three metadevice state databases with any metadevice, stripe, concat, or mirror.
When building two-way mirrors with DiskSuite, however, be sure that each physical disk has at least two metadevice state databases on it instead of just three total. If one of the disks were to die, the remaining disk must establish a majority, so it needs to have 50% of the replicas on it. If you put less than 50% of the replicas on the remaining good disk, there is a chance that all metadevice configuration information would be lost.
If you’re creating the databases by hand, do the following (assuming you’re mirroring things on /dev/rdsk/c0t0d0 and /dev/rdsk/c1t0d0, keeping your metadevice state databases on slice 7 on both disks):
/usr/sbin/metadb -a -c 2 /dev/rdsk/c0t0d0s7 /dev/rdsk/c1t0d0s7
The -a flag tells /usr/sbin/metadb to add the metadevice state database replicas to the specified slice, and the -c tells /usr/sbin/metadb how many replicas to put on each slice.
Add all the replicas to a slice at once.
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