[lug] Convert swap from raid0 to raid1

dio2002 at indra.com dio2002 at indra.com
Wed Jul 25 23:03:20 MDT 2007


> Why would you want to mirror swap space?  I can think of a few things
> that will help to make a box slow and that is one of them.  If your
> computer swaps it will have to make twice as many writes as it does now.

well according to some documentation i've read, it actually can be
beneficial.

1) although your writes are slower, your reads are faster and apparently
there are less writes than reads (don't know if i buy that but that's what
was written)

2) if your system is mirrored and one drive fails, your system will stay
up because your swap is mirrored.  otherwise your system goes down,
somewhat nullifying the use of mirroring.  of course you can reboot and be
up and running but unless someone is ready and waiting to reboot, your
system is down until that someone gets alerted and reboots.  and that
someone is going to be me :-)

if others can chime in on this i'm more than willing to hear their
thoughts.  i worried about the performance hit when i decided to go that
route but everything is a tradeoff.  availability versus performance in
this case.  if it's really going to degrade performance i imagine i'd just
can the mirroring on swap.

which brings up a question. as it stands now, swap is raid 0.  which means
that if one drive goes south when the system is booted, i believe that
would prevent the system from coming up.  i'll pull my drive and check
that in a second.

but before this thread gets completely hijacked, i want to try to solve my
original problem.  so if anybody has input on that. i'm game.





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