Re: multiple swap areas and RAID 1
On Wed, Aug 08, 2012 at 04:25:01PM +0300, Georgi Naplatanov wrote:
> Hi.
>
> I'm going to configure Debian GNU/Linux with software RAID 1 and I
> think to put swap area on RAID 1 (/dev/mdX), but someone told me
> that if the computer have multiple swap partition (e.g. /dev/sda2,
> /dev/sdb2) with equal priorities, linux kernel will mirror swap area
> between different devices. Is that true ? I mean kernel 2.6.32 and
> 3.2.x.
>
I suggest you consider whether you need redundancy for your swap
parition. What protection are you getting by putting it on RAID?
Basically, if a hard drive fails while the system is using swap, then
the swapped data is safe. If you didn't use RAID and that scenario
occurred, what would happen? Would a program crash? Is that acceptable
to you?
I've set up drives like this before:
/dev/sda1 - swap
/dev/sdb1 - swap
/dev/sda2 - RAID1 --> /dev/md0
/dev/sdb2 - RAID1 --> /dev/md0
I'm not claiming it's the best way. I save a little bit of hard drive
space (which is very cheap anyway), and I accept the risk of crashing a
program *if* the system is swapping while a hard drive dies (a pretty
low probability). Basically low risk and low payoff unless you're using
very expensive disks or have mission-critical applications running.
-Rob
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