Messages in this thread |  | | Date | Mon, 22 Jun 2009 18:31:13 +0200 | From | Ralf Gross <> | Subject | Re: io-scheduler tuning for better read/write ratio |
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Jeff Moyer schrieb: > Jeff Moyer <jmoyer@redhat.com> writes: > > > Ralf Gross <rg@stz-softwaretechnik.com> writes: > > > >> Casey Dahlin schrieb: > >>> On 06/16/2009 02:40 PM, Ralf Gross wrote: > >>> > David Newall schrieb: > >>> >> Ralf Gross wrote: > >>> >>> write throughput is much higher than the read throughput (40 MB/s > >>> >>> read, 90 MB/s write). > >>> > > >>> > Hm, but I get higher read throughput (160-200 MB/s) if I don't write > >>> > to the device at the same time. > >>> > > >>> > Ralf > >>> > >>> How specifically are you testing? It could depend a lot on the > >>> particular access patterns you're using to test. > >> > >> I did the basic tests with tiobench. The real test is a test backup > >> (bacula) with 2 jobs that create 2 30 GB spool files on that device. > >> The jobs partially write to the device in parallel. Depending which > >> spool file reaches the 30 GB first, one starts reading from that file > >> and writing to tape, while to other is still spooling. > > > > We are missing a lot of details, here. I guess the first thing I'd try > > would be bumping up the max_readahead_kb parameter, since I'm guessing > > that your backup application isn't driving very deep queue depths. If > > that doesn't work, then please provide exact invocations of tiobench > > that reprduce the problem or some blktrace output for your real test. > > Any news, Ralf?
sorry for the delay. atm there are large backups running and using the raid device for spooling. So I can't do any tests.
Re. read ahead: I tested different settings from 8Kb to 65Kb, this didn't help.
I'll do some more tests when the backups are done (3-4 more days).
Thanks, Ralf
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