Date: Tue, 16 Jun 2009 20:56:00 +0200
From: Ralf Gross <rg@stz-softwaretechnik.com>
To: linux-kernel@vger.kernel.org
Subject: Re: io-scheduler tuning for better read/write ratio
Message-ID: <20090616185600.GC7043@p15145560.pureserver.info>
References: <20090616154342.GA7043@p15145560.pureserver.info> <4A37CB2A.6010209@davidnewall.com> <20090616184027.GB7043@p15145560.pureserver.info> <4A37E7DB.7030100@redhat.com>
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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.

Ralf
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