Friday, June 10, 2005

disksuite metadb

Be aware that the optimal replica configuration may be different from
the one presented here, in the case that the data disks are also under
control of Solaris Volume Manager software and can contain state
database replicas.

Replica creation for the two-disk configuration (and disabling the quorum rule).

metadb -a -f -c 2 c0t0d0s7
metadb -a -c 2 c0t1d0s7
echo set md:mirrored_root_flag=1 >> /etc/system

If one of the disks is broken, Solstice DiskSuite software stops the
boot process. This reason for this is that, to successfully boot after
a failure, the majority of State Replica Databases must "survive." On
our two-disk mirror only three out of the six replicas would have
survived.

Servers with more than two disks should always have a third disk
configured with State Database Replicas. Twodisk workstations have to
be fixed manually, as described in the following example:

" State Database Replicas are configured on c0t0d0s7 and c0t1d0s7,
disk c0t0d0 fails.

" The boot process stops with a Solstice DiskSuite error message and
switches to Single User mode.

" Now the State Database Replicas on the failed disk have to be
unconfigured: metadb -d -f c0t0d0s7

" After the next reboot, partition the replacement disk exactly as in
the surviving disk.

" Having done that, you now can create new State Database Replicas on
the replacement disk: metadb -a -c 3 c0t0d0s7 "

Upon the next reboot, the mirror will be resynchronized.

Hint: If you have a two-disk system, create three State Database
Replicas on one disk, and four on the other one. Statistically there
is a 50 percent chance to successfully reboot after a failure without
manually using metadb. If you can tolerate unattended reboots after a
disk failure in a two-disk configuration, create the same number of
State Database Replicas on both disks and create this /etc/system
entry: set md:mirrored_root_flag=1. More information on this topic can
be found in the Sun BluePrints" publication "Configuring Boot Disks
With Solaris Volume Manager Software," (see:
http://www.sun.com/blueprints/1002/817-0407-10.pdf).

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