SUMMARY: ? mirroring swap space ?

From: alpha-osf-manager email acct <osf_at_python.corning.com>
Date: Mon, 19 May 1997 09:28:36 -0400 (EDT)

my original question was:
> i just ordered a mirror for my sys disk
> & was considering mirroring the swap disk also
> are there any strong pro/cons on this action

due to some of the responses i received,
i think i should clarify things a bit farther,
my swap space has been moved off my system disk onto its own separte disk
i want to avoid having a single-point-failure
ie: swap disk fail & system goes down
mirroring should resolve this problem,
but i was worried about a big performance hit
to sum up, the bset responses were:

>potential pro is that swap-in would be faster (reads
>alternate off of 2 different disks)
>
>The cons are that if you use LSM, setup & administration get more
>complex (unless you are using LSM anyway) it takes more disks, and it
>writes are potentially slower (has to write the block to 2 spindles
>instead of just one.
i'm not using lsm

>In my opinion, there is no performance penalty (I think LSM uses a round
>robin scheme to access the mirrors). There is a BIG PLUS for availability.
>If your primary swap is not working, you won't be able to go into multi
>user mode. We ordered a second system disk for two of our machines and will
>be mirrorring the root, swap and usr partitions (The whole system disk)
>because actually, it's the only thing that is not redundant in our systems.

>If your system is doing paging I/O, then having a mirror will
>prevent an I/O error from taking down the process or the system.

thanks to all who replied
Received on Mon May 19 1997 - 16:18:45 NZST

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