Date: Mon, 26 Apr 1999 16:08:28 +0100 (BST) From: Mr M P Searle <csubl@csv.warwick.ac.uk> To: naddy@mips.rhein-neckar.de (Christian Weisgerber) Cc: freebsd-questions@freebsd.org Subject: Re: writing slower with SoftUpdates Message-ID: <199904261508.QAA02883@primrose.csv.warwick.ac.uk> In-Reply-To: <7ftnto$top$1@mips.rhein-neckar.de> from Christian Weisgerber at "Apr 25, 99 02:34:00 am"
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> Dan Nelson <dnelson@emsphone.com> wrote: > > > If these are in fact identical drives, I would start looking at the > > mode pages on the first drive to see if you have write caching turned > > on. Softupdates usually prefers to cache data itself, and you can get > > degraded performance if the drive is doing caching too. > > In what way do soft updates perform additional caching? Writes are not made immediately, but are delayed in the same way that a HD cache does. > And why should this interact badly with drive caching? I don't know, but the drive cache doesn't seem to make any difference to the speed when using soft updates. (the HD's cache is so much smaller that the amount of memory buffers soft updates can use it won't make any difference.) > Disabling the > drive's write caching seems like an excellent way to cripple the drive > to me. > Soft updates is also not just a dumb cache like the HD cache, but knows about the file system structure. This makes it much safer than running either the old async file system or a HD cache as the file system is unlikely to be seriously corrupted in a crash. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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