Date: Mon, 24 Nov 1997 21:13:47 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: "John S. Dyson" <toor@dyson.iquest.net> Cc: hackers@FreeBSD.ORG, reyesf@super.zippo.com Subject: Re: Optimizing HD I/O. What size to use to read/write? Message-ID: <XFMail.971124211336.shimon@Simon-Shapiro.ORG> In-Reply-To: <199711180932.EAA01115@dyson.iquest.net>
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On 18-Nov-97 John S. Dyson wrote: > Francisco Reyes said: >> I am going to start working on a program which will be heavy on I/O. >> I was wondering what would be a good size to read/write at a time. >> >> What is the minimun block size FreeBSD allocates? 4K? 8K? Is it HD >> dependent? >> > One more comment, if you are doing sequential I/O, you really don't > want > to do read/writes less than 4K-8K. You are likely into diminishing > returns beyond 8K. I'd say it applies to random access even more. Especially if there is more than one client for the disk I/O. On SCSI, up to about 8K, the dominant factor is bus handling, data is a small fraction. After 8K data starts showing up (and this is where wide/ultra/shmultra start making a difference). > > -- > John > dyson@freebsd.org > jdyson@nc.com If Microsoft Built Cars: There would be an "Engine Pro" with bigger turbos, but it would be slower on most existing roads. Sincerely Yours, Simon Shapiro Shimon@Simon-Shapiro.ORG Voice: 503.799.2313
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