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    SubjectRe: Poor performance during disk writes
    On Tue, Dec 18, 2001 at 06:42:49PM +0100, Gérard Roudier wrote:
    >
    >
    > On Tue, 18 Dec 2001, Andre Hedrick wrote:
    >
    > > File './Bonnie.2276', size: 1073741824, volumes: 1
    > > Writing with putc()... done: 72692 kB/s 83.7 %CPU
    > > Rewriting... done: 25355 kB/s 12.0 %CPU
    > > Writing intelligently...done: 103022 kB/s 40.5 %CPU
    > > Reading with getc()... done: 37188 kB/s 67.5 %CPU
    > > Reading intelligently...done: 40809 kB/s 11.4 %CPU
    > > Seeker 2...Seeker 1...Seeker 3...start 'em...done...done...done...
    > > ---Sequential Output (nosync)--- ---Sequential Input-- --Rnd Seek-
    > > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --04k (03)-
    > > Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU
    > > 1*1024 72692 83.7 103022 40.5 25355 12.0 37188 67.5 40809 11.4 382.1 2.4
    > >
    > > Maybe this is the kind of performance you want out your ATA subsystem.
    > > Maybe if I could get a patch in to the kernels we could all have stable
    > > and fast IO.
    >
    > I rather see lots of wasting rather than performance, here. Bonnie says
    > that your subsystem can sustain 103 MB/s write but only 41 MB/s read. This
    > looks about 60% throughput wasted for read.

    Uh, well, um, what drive is he writing too?? He could very well have 2 gig
    of memory in this box and half the writes were cached. 41MB/s seems
    reasonable for most common IDE disks. Of course I know Andre has some
    rather 'uncommon' IDE drives :P

    Does bonnie actually do any sort of 'sync' operation to ensure data
    writen is on the disk? Is that 100mb/sec write real, or just because of
    block layer caching?

    >
    > Note that if you intend to use it only for write-only applications,
    > performance are not that bad, even if just dropping the data on the floor
    > would give you infinite throughput without any difference in
    > functionnality. :-)
    >
    >
    > Gérard Roudier
    > Not CEO, not President of anything.
    >
    > > Regards,
    > >
    > >
    > > Andre Hedrick
    > > CEO/President, LAD Storage Consulting Group
    > > Linux ATA Development
    > > Linux Disk Certification Project
    >
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    --
    Troy Benjegerdes | master of mispeeling | 'da hozer' | hozer@drgw.net
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