[SunHELP] more on mirroring

[Scanlan, Brian (5188)]

Hey,

FAQ 2373 on Sunsolve.sun.com might help ya out...

The way I've done it before, 'cos it seemed to have the least
nonsense involved (somebody please point out if this has any
flaws...) was to comment out the Disksuite relevant
lines in /etc/system and change the lines for the relevant
filesystems in /etc/vfstab to just use the /dev/dsk entries.

Then when ya have the replacement disk, just go through the 
installation of Disksuite process.

Have backup /etc/system and /etc/vfstab in place at all time, 
you might even have those altered /etc/system and /etc/vfstab's
in place so you're not attempting this the first time when
your disk fails. ;)

This way seemed to be the quickest to describe over the phone to
a panicy clueless sysadmin, oh to be back in support. ;)

Brian.

-----Original Message-----
From: Tom Lieuallen [mailto:toml at engr.orst.edu]
Sent: 24 January 2001 16:42
To: SunHELP at sunhelp.org
Subject: [SunHELP] more on mirroring



I saw the question and answers about mirroring in the last digest.
I'm assuming that by having two disk bays and selling two disks
with the 220 and 420's was so that people could and would mirror
the boot disk.

But, from my perusal of the disksuite instructions on mirroring,
I'm not sure what the recommended setup would be.

The problem I have is with the metadb's.  If you only have two
disks, then they recommend putting at least two metadb's on each
disk.  If one disk fails, it can continue to run with half of the
databases.  However, if I read correctly, at boot time, it has to have
half plus one or it won't boot.

So, does this mean that if you lose a disk in this setup, you have to
replace it on the live system and let the mirroring setup the new disk
before you reboot?  I assume one would have to manually remove the
metadb's from the dead disk and partition the new disk before the
mirror sync could or should happen.

Or, does it mean that if you lose a disk, you boot in single user off
the remaining disk; remove the mirror config, boot again, and rebuild
the mirror with a new second disk?  If it is this complex, then I
question whether it is worth the effort.

Maybe the best question is whether people have good or bad experiences
with mirroring the boot disk with disksuite, especially with only two
disks, and what the procedure is if you lose one of them.

thank you

Tom Lieuallen
Oregon State University
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