Date: Thu, 01 Sep 2011 02:01:46 -0700 From: perryh@pluto.rain.com To: freebsd@jdc.parodius.com Cc: dmagda@ee.ryerson.ca, freebsd-stable@freebsd.org, dart@es.net Subject: Re: Unable to shutdown Message-ID: <4e5f49fa.2qH1H6gV7TIdZYiD%perryh@pluto.rain.com> In-Reply-To: <20110831071207.GA95960@icarus.home.lan> References: <CAN6yY1s3x1ojxh-Dx9Ht=L8M4frohLXcMLNgz%2BzgtBCDodBdsg@mail.gmail.com> <uh78vqd9u8e.fsf@P142.sics.se> <4E5BF15F.9070601@es.net> <CAN6yY1u6ZshVZT2DwaQ2Et7Y1JvNA8q%2BFj5os4SmK4=7=Z77vg@mail.gmail.com> <f0ffdf9eccf14f42ee24f0982bb0fc4b.squirrel@webmail.ee.ryerson.ca> <20110830214832.GA87354@icarus.home.lan> <CAN6yY1upYKW9e3mmED11pTXk%2BVO1KduPy-boWTr7m9S42jUKWw@mail.gmail.com> <20110830234323.GA88936@icarus.home.lan> <CAN6yY1v%2ByqZTkX=XjAoLJWNuf%2Bz6OwR-s2sfdGuGk_RXwBK_VA@mail.gmail.com> <20110831071207.GA95960@icarus.home.lan>
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Jeremy Chadwick <freebsd@jdc.parodius.com> wrote: > On Tue, Aug 30, 2011 at 11:04:43PM -0700, Kevin Oberman wrote: > > ... the standrad does not specify EXACTLY what triggers a > > transition from standby to ready (PM2 to PM0). Only that it is > > something that requires media access. A write does not > > necessarily require media access if you define "media" as the > > disk platter. > > You're correct -- "media access" could mean, literally, "accessing > the platter" OR it could mean "LBA read/write I/O". Then comes > into question whether or not the drive returning something from > its on-board cache would count as "media access" or not. > > T13 should probably clarify on this point, and this is one I do > not have an answer for myself. I strongly believe "media access" > means "LBA read/write I/O" and regardless if it's data that's in > the on-board cache on the disk or not. I wonder if this behaviour > varies per drive model. Given a standard which is, shall we say, "open to interpretation", I think the liklihood approaches 100% that it has been interpreted differently by different manufacturers -- or even by different firmware authors within a single manufacturer. I would be amazed if the behaviour did _not_ vary among drive models.
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