Date: Thu, 21 Sep 2000 17:02:57 +0200 (CEST)
From: Soren Schmidt <sos@freebsd.dk>
To: Stephen.Byan@quantum.com (Stephen Byan)
Cc: mbendiks@eunet.no ('Marius Bendiksen'), fs@FreeBSD.ORG, sos@FreeBSD.ORG, freeBSD-scsi@FreeBSD.ORG
Subject: Re: disable write caching with softupdates?
Message-ID: <200009211502.RAA92422@freebsd.dk>
In-Reply-To: <8133266FE373D11190CD00805FA768BF055BD1D6@shrcmsg1.tdh.qntm.com> from Stephen Byan at "Sep 21, 2000 07:08:37 am"
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It seems Stephen Byan wrote: > Marius Bendiksen [mailto:mbendiks@eunet.no] wrote: > > > > Contrast this 10% performance hit versus what you get when > > you disable > > > caching entirely. > > > > I think you will see that on some drives, this may have a greater > > performance impact than not caching at all. > > Perhaps Søren will be kind enough to run the experiment? I'd be interested > in analyzing cases in ATA drives where flushing delivers worse performance > than disabling cache. Well, I have been toying a bit with this, so far results are just timing of a make -j16 buildworld on two IBM DJNA drives (ie no tags) with varius setups. ATA driver "as is": 3602.63 real 0.00 user 2865.62 sys ATA driver with flush cache on "BIO_ORDERED": 3964.18 real 0.00 user 2870.09 sys ATA driver with write cache disabled: 4423.30 real 0.00 user 2871.87 sys So, having the write cache there definitly is a win. I'll try this on TWO IBM DTLA drives with tags enabled and see what gives.. Anything else you want me to mess with now we are at it ? -Søren To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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