From: Gene Matthews (gene@mmc-inc.com)
Date: Thu Aug 22 2002 - 13:03:46 EDT
Hello all,
I have an ultra 10 (Solaris 2.6) that currently has two 8 gig disks
(mirrored). When mirroring was setup, only one state database was
placed on each disk.
My basic plan is to halt the system and replace the slave 8 gig disk
with one of the new 20 gig disks (I have the patches on to use the
larger disks). Now when the system comes back up it will only find one
state database, which is exactly half of what it thinks should be there.
In reading the metadb man page, it says:
Replicated databases have an inherent problem in determining
which database has valid and correct data. To solve this
problem, DiskSuite uses a majority consensus algorithm.
This algorithm requires that a majority of the database
replicas agree with each other before any of them are
declared valid. This algorithm requires the presence of at
least three initial replicas which you create. A consensus
can then be reached as long as at least two of the three
replicas are available. If there is only one replica and the
system crashes, it is possible that all metadevice
configuration data may be lost.
I have no idea if the system originally had 3 state db's as the above
implies it had to have to work. I have inherited about 8 systems that
are set up with only one state db per disk. Can it reach consensus with
only one of the two state databases available? Will I be able to get
the system back up with only one state db?
Would I be better off just breaking the mirrors and "undoing" all the
DiskSuite stuff ? If so, would the following accomplish putting the
system back to using normal device files:
1- boot into single user mode
2- umount everything that I can (all but / and /usr I guess)
3- update /etc/vfstab to use the old device files, e.g.
/dev/dsk/c0t0d0s4 vs /dev/md/dsk/d4)
4- mount all the f/s again and verify all the data is there
5- for /usr and /, update /etc/vfstab as in step 3, then comment out
all the Disksuite stuff in /etc/system
6- reboot
I guess, in a nutshell, the real questions are-
1- If I leave it as is (mirrored w/ one state db per disk) and I halt
the system, remove one disk and replace it with a new one, will it boot
up?
2- If the answer to 1 is no, will the steps above successfully "remove"
DiskSuite from being used?
Thanks,
Gene
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