>
> > No-one swaps to md devices, except raid-1 and that only, if one really,
> > really needs it. It's just too slow.
>
> Is it really that slow? The md-devices are faster than a regular disk (I
use
> RAID 5).
<snip>
> faster than a single disk: yes.
> faster than normal swapping: no.
> Normally, if you have the option to swap to md devices, you have more
> than one disk. The non-md way of swapping would then be:
> root# grep swap /etc/fstab
> /dev/sda9 swap swap defaults,pri=1 0 0
> /dev/sdb9 swap swap defaults,pri=1 0 0
> /dev/sdc9 swap swap defaults,pri=1 0 0
>
> i.e. somthing like a raid0 device setup. You know that raid0 is fastest
> of all raid levels when the access pattern is something like 50-50 r-w
> and small blocks. So any other raid level used will slow things down.
Alright, but this approach is still vulnerable to a disk crash. I one of the
disks currently used for swapping goes down, the machine goes with it. At
least according to Jacobs HOWTO... Maybe it's a question of choosing between
swap speed and stability. In my case it's more important that the machine
can suffer a disk failure without going down.
Best regards
/Johan Ekenberg
