[ale] who is eating my drive

[Jim Kinney]

On Tue, May 31, 2011 at 3:04 PM, Pat Regan <thehead at patshead.com> wrote:

> On Tue, 31 May 2011 14:49:53 -0400
> Jim Kinney <jim.kinney at gmail.com> wrote:
>
> > swap notes: NEVER put swap on a raid5. If you must park swap on a
> > RAID rig, mirrored partitions are OK. If swap gets hosed, the box
> > crashes. The RAID5/6 writes for swap are performance killers. Swap
> > will do it own striping so don't bother doing a raid10. multiple swap
> > parts on multiple drive spindles is a good thing. Say 8G RAM and 4
> > 1TB drives, set up a 4G swap on each of the drives.
>
> Putting swap on RAID also means that your server won't go down due to a
> disk failure.
>

Swap on RAID5/6 means during a rebuild the disk IO times out on swap
retrieval and the kernel panics thinking the swap is down.

>
> I complain about the poor write performance of RAID 5 and 6 all the
> time, but I'd rather have slow swap the few times I actually need any
> swap at all instead of having my server fail when a disk goes bad :)
>
> > I haven't dug in the kernel code itself, but supposedly, swap over 2G
> > total size is not relevant. By the time it's being used the box is
> > crawling anyway.
>
> I've swapped pretty deep with rather large tmpfs file systems.  You can
> probably fill up as much swap as you like with those without the tmpfs
> getting much slower than a real file system.
>
> It all depends on what is actually being swapped out...
>
> Pat
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-- 
-- 
James P. Kinney III

As long as the general population is passive, apathetic, diverted to
consumerism or hatred of the vulnerable, then the powerful can do as they
please, and those who survive will be left to contemplate the outcome.
- *2011 Noam Chomsky*
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