Hibernate with LVM Swap
pjones at redhat.com
Tue Jun 13 21:23:30 UTC 2006
On Tue, 2006-06-13 at 13:36 -0600, Lamont R. Peterson wrote:
> > Moreover, there isn't a compelling reason *not* to do it. This
> > hypothetical performance-while-swapping argument you've got just isn't
> > reality. You're not CPU bound when you're swapping. You're I/O
> > limited, and most of the limit isn't time on the host bus, it's disk
> > seeks. I really doubt if LVM will make any significant difference --
> > measurable difference, that is, much less noticeable by a human -- at
> > all.
> Of course. Yes, swapping is not memory or CPU bound, it is I/O bound, as you
> state. However, I wasn't talking about LVM code overhead, I was talking
> about drive seek overhead in heavy swapping situations.
> If you are doing heavy swapping with a swap partition, the on disk storage is
> contiguous and, therefore, you will have less distance to travel when
That's just as true as on LVM. If I build a LV to put swap on that's
comprised of several PVs which aren't contiguous, then sure, it's not
contiguous. At the same time, if I make 7 partitions that are 100M each
and activate them all, I've got 7 discontiguous areas.
In both cases it's "if I set my machine up stupidly, swaping sucks even
more than normal".
> On LVM, the PEs could be spread around the disk more widely (i.e.
> non-contiguous), so the heads will have farther to go. If you're *really*
> lucky, your heavy swapping pattern will let you alternate (or rotate, if that
> word fits better) around each of the disks with PEs backing your swap LVs
> LEs. But, the likelyhood of that working out is very small.
It's about as small as actually getting into this contrived situation in
the first place...
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