Re: Linux I/O schedulers - CFQ & random seeks

On 3/4/11 11:03 AM, Wayne Conrad wrote:
> On 03/04/11 10:34, Glyn Astill wrote:
> > I'm wondering (and this may be a can of worms) what peoples opinions
> are on these schedulers?
>
> When testing our new DB box just last month, we saw a big improvement
> in bonnie++ random I/O rates when using the noop scheduler instead of
> cfq (or any other). We've got RAID 10/12 on a 3ware card w/
> battery-backed cache; 7200rpm drives. Our file system is XFS with
> noatime,nobarrier,logbufs=8,logbsize=256k. How much is "big?" I
> can't find my notes for it, but I recall that the difference was large
> enough to surprise us. We're running with noop in production right
> now. No complaints.
>
Just another anecdote, I found that the deadline scheduler performed the
best for me. I don't have the benchmarks anymore but deadline vs cfq
was dramatically faster for my tests. I posted this to the list years
ago and others announced similar experiences. Noop was a close 2nd to
deadline.

XFS (noatime,nodiratime,nobarrier,logbufs=8)
391GB db cluster directory
BBU Caching RAID10 12-disk SAS
128GB RAM
Constant insert stream
OLAP-ish query patterns
Heavy random I/O