Greetings,
I'm just experimenting with software RAID on Linux for the first time,
and have been reading what I can find on the Web about the current state
of Linux RAID support. The latest version of the Software-RAID.HOWTO
that I could find (v. 0.90.7 19th of January 2000) had this to say about
swapping to a RAID device:
---8<---
There has been a lot of discussion about whether swap was stable on RAID
devices. This is a continuing debate, because it depends highly on other
aspects of the kernel as well. As of this writing, it seems that
swapping on RAID should be perfectly stable, except for when the array
is reconstructing (eg. after a new disk is inserted into a degraded
array). When 2.4 comes out this is an issue that will most likely get
addressed fairly quickly, but until then, you should stress-test the
system yourself until you are either satisfied with the stability or
conclude that you won't be swapping on RAID.
You can set up RAID in a swap file on a filesystem on your RAID device,
or you can set up a RAID device as a swap partition, as you see fit. As
usual, the RAID device is just a block device.
--->8---
Since this was written a few months ago, and we're several releases into
2.4.x, I was wondering what the concensus of opinion was today? Is it
safe to use a RAID-1 mirror as a swap device? Is there still a stability
``issue'' with the released 2.4.x kernels during array reconstruction?
And what specifically is/was this issue anyway? An older HOWTO mentioned
that the md device would sometimes allocate kernel memory to service a
write, which caused problems when the kernel was trying to write a page
to swap so that it could free it up to service another allocation. I
presume this has been addressed in the latest code -- so what's the
remaining issue with reconstruction?
-- Kaelin
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