[dm-devel] [PATCH 1/2] dm-kcopyd: introduce per-module throttle structure
Mikulas Patocka
mpatocka at redhat.com
Tue Jun 7 17:50:16 UTC 2011
On Fri, 3 Jun 2011, Joe Thornber wrote:
> On Thu, Jun 02, 2011 at 03:55:16PM -0400, Mikulas Patocka wrote:
> > > iv) you haven't explained how the sys admin works out the correct
> > > throttle value.
> >
> > There is no "correct" value. The "correct" value depends on how important
> > is copying itself v.s. other i/o.
>
> So who is going to set this? Do you really have no advice for them
> beyond 'there is no correct value'?
I did some tests. I did some random and sequential I/O on the same disk
while mirror was resynchronizing. The result is this:
random read:
mirror throttle / IOs per second
100% 94
75% 113
50% 127
25% 145
idle 160
sequential read:
mirror throttle / throughput MB/s
100% 104
75% 118
50% 122
25% 127
idle 134
Mikulas
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