Date: Mon, 4 Mar 2002 20:52:58 -0700 From: "Kenneth D. Merry" <ken@kdm.org> To: Carl Reisinger <cer@mirapoint.com> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: Writing > 64KB records to SCSI Tape, FreeBSD 4.1 (?) Message-ID: <20020304205257.A13402@panzer.kdm.org> In-Reply-To: <200203050202.AOD05455@mail.mirapoint.com>; from cer@mirapoint.com on Mon, Mar 04, 2002 at 06:03:22PM -0800 References: <200203050202.AOD05455@mail.mirapoint.com>
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On Mon, Mar 04, 2002 at 18:03:22 -0800, Carl Reisinger wrote: > I would like to write records of 128KB to a SCSI tape device > (DLT 7 or 8000, LTO). > > While MAXPHYS is 128KB, the code in kern_physio:physio will > adjust the max size based on the value of dev->si_iosize_max. > > It my case it appears that this value is 0 (or < PAGE_SIZE), > so physio will set si_iosize_max to DFLTPHYS which is > defined to be 64KB. In any case DFLTPHYS is the limit I am > hitting. > > This in turn will cause the 128KB write to be broken into > two 64KB writes, which just doesn't work for me. > > The best solution, for me, would be a change to scsi_sa.c > that will set si_iosize_max for the device. > > Can anyone help? 64K is pretty much the lowest common denominator as far as transfer size goes. I believe that's pretty close to what an Adaptec 1542 can handle, so that's why we've left it at that size. (From a CAM standpoint that is.) I would suggest just bumping si_iosize_max up to 128K in your copy of the sa(4) driver and see if that does the trick. > NOTE: While most of the kernel is based on 4.1-STABLE, I > believe the CAM subsystem and scsi_sa has been lifted from > 4.3. (The behaviour is the same under 4.5) Sounds "interesting". :) Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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