Date: Thu, 3 Jun 1999 19:34:43 +0200 (CEST) From: Wilko Bulte <wilko@yedi.iaf.nl> To: zzhang@cs.binghamton.edu Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: The choice of MAXPHYS Message-ID: <199906031734.TAA00693@yedi.iaf.nl> In-Reply-To: <Pine.GSO.3.96.990603101914.28480A-100000@sol.cs.binghamton.edu> from Zhihui Zhang at "Jun 3, 1999 10:40:10 am"
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As Zhihui Zhang wrote ... > > The value of MAXPHYS is chosen to be 64K for the maximum raw I/O transfer > size. I am wondering why it is not set larger. The maxcontig value of FFS > is default to be 16, which means 16*8192 or 128K bytes (twice as big as > 64K) . If we raise the value of MAXPHYS, we can put more data blocks of a > big file contiguously on the disk (perhaps even more than 16 blocks to > achieve better performance). Am I right? Is there any limit of the value > of MAXPHYS? The 64kB limit is a limitation of older SCSI cards. My primary objective to have a > 64kB MAXPHYS is to have larger blocksizes on tape. Especially DLT drives love that ;-) | / o / / _ Arnhem, The Netherlands - Powered by FreeBSD - |/|/ / / /( (_) Bulte WWW : http://www.tcja.nl http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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