[4841] in linux-scsi channel archive
Re: 2K sectors
daemon@ATHENA.MIT.EDU (Harvey Fishman)
Thu Oct 8 13:52:29 1998
Date: Thu, 8 Oct 1998 11:10:29 -0400 (EDT)
From: Harvey Fishman <fishman@panix.com>
To: William Brioschi <capo@writeme.com>
cc: Linux SCSI mailing list <linux-scsi@vger.rutgers.edu>
In-Reply-To: <m0zRBHG-00022yC@fire.casa.brioschi.net>
On Thu, 8 Oct 1998, William Brioschi wrote:
> I have a 640M magneto-optical drive which uses 2K blocks.
> Of course, Linux (2.0.29) complains about the unsupported sector size.
>
> I _have_ to use it, mainly for backup purposes. Performance is not an issue:
> I would be happy with a 100K/sec.
>
> I think there are three possibilities to be able to access a cartdridge:
> 1) make Linux scsi disk and low level drivers digest the big sectors; this is
> probably not a very good idea, unless it's already been done in a newer
> kernel... has it?
> 2) make the drive understand I need 1K sectors; the SCSI-HOWTO says something
> about the MODE SELECT command, how can I send it? will it work? will I have
> to reformat the cartdridges (which come preformatted at low level with a 2K
> sector)? how will I lo level format a cartdridge?
> 3) use the device in raw, sequential mode (through tar or something like that),
> probably using the SCSI generic driver; I haven't tried this yet, is it
> possible? should I do something particular or can I simply do a
> "tar cf /dev/sga"?
>
> Or, is there a simple solution I am not able to see?
My experience with the M2513a and 640 MB media is that tar works fine but
mount does not. So you can write in raw sequential mode but not anything
higher. You cannot reformat the media to a different sector size as MO
disks are sort of hard sectored; the soft-sectoring information is there,
but there are also physical sector separators on the disk. But Maxell and
probably Fujitsu also did offer 540 MB media. These were media made with
the same technology as the 640 MB ones but with 512 byte sectors. As you
shrink the sector size, the space wasted for overhead goes up and the total
capacity goes down. If you need to work at high level, perhaps these would
serve the purpose. Contact your supplier or Maxell or Fujitsu for ordering
details. Or else use tar raw as I do. The drive does handle 230 MB media
fine, and these have 512 byte sectors so there is no problem with working
at the file level.
One thing though; I use 2.1.106 (because no later kernel will properly
handle the IBM ECS and allow me to play NetHack comfortably) and have never
tried this with a 2.0 kernel. I had moved to 2.1 before I got the drive.
Harvey
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Harvey Fishman |
fishman@panix.com | A little heresy is good for the soul.
718-258-7276 |
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