Date: Mon, 2 Mar 1998 17:23:50 -0600 From: Karl Denninger <karl@mcs.net> To: David Kelly <dkelly@hiwaay.net> Cc: scsi@FreeBSD.ORG Subject: Re: SCSI low level format, good or bad Message-ID: <19980302172350.11640@mcs.net> In-Reply-To: <199803021206.GAA26129@nospam.hiwaay.net>; from David Kelly on Mon, Mar 02, 1998 at 06:06:27AM -0600 References: <karl@mcs.net> <199803021206.GAA26129@nospam.hiwaay.net>
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On Mon, Mar 02, 1998 at 06:06:27AM -0600, David Kelly wrote: > Karl Denninger writes: > > > > I've seen a non-trivial number of disks come off the factory line with > > non-optimal formats. I don't know if its a temperature tolerance thing or > > what, but this has been my experience. > > What do you consider a non-optimal format? One which generates errors after short periods of being online (small numbers of unrecoverable block errors), among other things. Then there is the entire mode page issue. > Does Adaptec's low level format mess with the SCSI mode pages? If so, > reformatting might "optimize" the disk. I've observed the default for > WCE and other options varies according to where the disk came from, not > by manufacturer. Yes. I have a rather old utility which works with Adaptec SCSI host adapters which can change most of the mode pages that are "interesting". Its not perfect, but it works for a lot of stuff that otherwise is "immutable" without a lot of screwing around. > I stick by the "if it ain't broke, don't fix it" reasoning. There is no > telling exactly how they format the drive at the factory. No telling > what additional hardware monitors are attached to the drive. You'll > notice most all drives have additional connectors and test points for > *something*. > > In fact there is no telling exactly what happens when you "low level" > format the drive yourself. With any luck it will take the factory defect > list (not block list, but lowest level bit error position from index, > remember MFM and RLL disks?) as gospel and try to arrange blocks around > that. The problem appears, in many cases, to be temperature tolerance. This is why its very, very important to run a drive in the final enclosure with all covers, etc in place for a couple of hours before you try to low-level format it. I know that with today's positioners and such this is never supposed to be necessary. Tell that to the disks that I've had to format, but once doing so have run for *years* without a single block error. -- -- Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin http://www.mcs.net/ | T1's from $600 monthly to FULL DS-3 Service | NEW! K56Flex support on ALL modems Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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