Friday, June 10, 2005

Disappearing metadb entries

TOPIC: Disappearing metadb entries

== 1 of 1 ==
Date: Mon 6 Jun 2005 16:48
From: Darren Dunham

UNIX admin wrote:
> This brings up an interesting design question though: I was taught in
> courses to use 3 replicas per disk, however as one adds more and more
> disks, this number becomes suboptimal because of quorum. What do you
> think the sweet spot would be when going beyond RAID1 (add another RAID5
> and three disks) and two-way mirroring?

The following appears in the SVM documentation:
http://docs.sun.com/app/docs/doc/816-4520/6manpiei3?a=view

[...]
To avoid single points-of-failure, distribute state database replicas
across slices, drives, and controllers. You want a majority of replicas
to survive a single component failure. If you lose a replica (for
example, due to a device failure), problems might occur with running
Solaris Volume Manager or when rebooting the system. Solaris Volume
Manager requires at least half of the replicas to be available to run,
but a majority (half + 1) to reboot into multiuser mode.

A minimum of 3 state database replicas are recommended, up to a maximum
of 50 replicas per Solaris Volume Manager disk set. The following
guidelines are recommended:

For a system with only a single drive: put all three replicas on one
slice.

For a system with two to four drives: put two replicas on each drive.

For a system with five or more drives: put one replica on each drive.
[...]

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