Re: Poor performance during disk writes

[Troy Benjegerdes <hozer@drgw.net>]

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
-----"If this message isn't misspelled, I didn't write it" -- Me -----
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