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SubjectRE: question about scsi generic behavior

Hardcoding of block size to 512 bytes for disk devices is what currently
either the block device driver or the sd driver is doing. Because, if
I run dd to the same device using the corresponding block device (sde)
it runs fine. So, I feel that either the sg driver or the block device
or sd driver needs to be fixed.
One more thing is that, sg driver can find out from READ_CAPACITY the
block size on the device. So, if dd specifies bs=4096 and count=1, then
accordingly, the sg driver should set the count to 8 and bs to the bs of
the device. IMHO, untimately, the total transfer length is what matters.


> -----Original Message-----
> From: David Chambliss []
> Sent: Friday, June 08, 2001 4:49 PM
> To:
> Cc:;
> Subject: Re: question about scsi generic behavior
> I think you need to set bpt=8 .
> It is possible to set some drives to block sizes other than
> 512 bytes, and
> hardcoding 512 is not a good idea, especially in code that
> might last a
> while. In a few years we might have 4096-byte blocks to let
> the drives use
> more powerful error correcting codes.
> David Chambliss
> Research Staff Member, Computer Science /Storage Systems
> IBM Research Division
> (408) 927-2243 (TL 457-2243)
> FAX (408) 927-3497
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