Date: Wed, 28 Feb 2007 10:47:02 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "M. Warner Losh" <imp@bsdimp.com> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/usb umass.c Message-ID: <43716.1172659622@critter.freebsd.dk> In-Reply-To: Your message of "Wed, 28 Feb 2007 03:30:55 MST." <20070228.033055.-135505832.imp@bsdimp.com>
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In message <20070228.033055.-135505832.imp@bsdimp.com>, "M. Warner Losh" writes : >Others have observed that the number of sectors on a disk should be >even. Therefore if maxsectors returned is even, it implies an odd >number of sectors and should be adjusted. Hmm, although generally true for present day disks, I don't think it is universal enough that I would want to rely solely on it. >number of sectors and should be adjusted. That might be an even >easier path to follow... I'm never sure when one can schedule >additional I/O inside of cam... Neither am I. Thinking about it, geom_disk might be a better place for it anyway. That way we could postpone announcment of the disk to GEOM tasting until we know it can actually answer a request. Spin-up and other long delays will not affect the system nearly as hard as they can today. Early on I thought about a mandatory "read first & last sector" check for all providers created in geom, but dropped it due to the excessive shake, rattle and roll of big diskfarms and complex layouts. But it might be a good idea to add it in a reduced form applied to all providers which come in at rank==1 (that way we would not do it for partitions, slices, mirrors etc). -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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