Date: Wed, 17 Jun 1998 05:31:18 -0400 (EDT) From: Peter Dufault <dufault@hda.com> To: dan@math.berkeley.edu (Dan Strick) Cc: freebsd-scsi@FreeBSD.ORG, dan@math.berkeley.edu Subject: Re: the scsi pass through ioctl Message-ID: <199806170931.FAA15033@hda.hda.com> In-Reply-To: <199806170158.SAA20496@math.berkeley.edu> from Dan Strick at "Jun 16, 98 06:58:31 pm"
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> 1) Can someone explain the timeout member of the scsireq struct > used for the SCIOCCOMMAND (scsi command pass through) ioctl()? > > I would guess it sets the time period after which an incomplete > scsi command will be cancelled without returning scsi status > and that the SCCMD_TIMEOUT code will be returned in the > retsts member of the scsireq struct. > > Can someone confirm this? > Can someone tell me in what units the timeout is specified? > Seconds? Milliseconds? Days? Endless Summers? Yes - milliseconds. > > 2) A long time ago someone said in a FreeBSD mailing list that you > could trash your disk contents by attempting scsi pass through > commands while the disk was also doing normal file system I/O. > > Does anyone recall why this might have been the case and know > if it might still be the case? I can think of reasons why I > might want to do "harmless" scsi commands on an active disk. I don't know of any reason and I did test it on active disks. Harmless scsi commands should be fine. Any part of the system not heavily used and not regression tested is likely to have problems and should be used cautiously at first. Formatting disks, I/O bypassing the buffer cache, and so on must be avoided... Peter -- Peter Dufault (dufault@hda.com) Realtime development, Machine control, HD Associates, Inc. Safety critical systems, Agency approval To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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