[4433] in linux-scsi channel archive
Re: Bad blocks: How many?
daemon@ATHENA.MIT.EDU (Dr. Michael Weller)
Wed Jul 22 05:04:19 1998
Date: Wed, 22 Jul 1998 10:52:35 +0200 (MESZ)
From: "Dr. Michael Weller" <eowmob@exp-math.uni-essen.de>
To: Jon Lewis <jlewis@inorganic5.fdt.net>
Cc: Tim Robinson <timr@sykes.demon.co.uk>, linux-scsi@vger.rutgers.edu
In-Reply-To: <Pine.LNX.3.95.980721230925.1253r-100000@tarkin.fdt.net>
On Tue, 21 Jul 1998, Jon Lewis wrote:
> On Tue, 21 Jul 1998, Dr. Michael Weller wrote:
>
> > > I've ever seen scsi-config report anything in the grown list. Just
> > > recently, I was setting up some Micropolis 1991's and 3 were "bad". 1
> > > could not be formatted without lots of errors locking up the system. 2
> > > were formattable but generated unrecoverable read errors when tested. I
> > ---------------------------------------
> >
> > Uhmm.. Did you actually enable disk certify (verifying) with the format
> > command? Well, I think it is default anyhow. Nevertheless it is up to the
>
> You mean mke2fs -c? Probably not on the first format. I know I did later
> after I knew I had problems, and after I turned on AWRE and ARRE.
No, I meant during the low level SCSI format. The SCSI FORMAT_UNIT command
comes in two flavours, one short command and one long. The long version
has a bit which enables media certify. The disk drive is expected then to
do extensive media checks during the format. Other bits control if grown
defects are reset and new defects detected during the format are added to
the grown lists and so on.
The short version has basically no choices.. just 'go format using
sensible defaults'. Usually sensible defaults includes making a media
certify and add any new defects to the grown defects list. But there is no
guarantee. scsiinfo-1.7 also allows you to format using these bits. Alas,
I had to learn most disks just understand the simple, unflexible format
command.
mke2fs -c just reads (maybe writes) all sectors. Now, the disk might
use this to reallocate sectors on error, but with SCSI mke2fs -c should
have no user visible effect. Also, the disk format is expected to make
more intensive tests than this.
Michael.
--
Michael Weller: eowmob@exp-math.uni-essen.de, eowmob@ms.exp-math.uni-essen.de,
or even mat42b@spi.power.uni-essen.de. If you encounter an eowmob account on
any machine in the net, it's very likely it's me.
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