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From: martin@idca.tds.PHILIPS.nl (Martin Peeters)
Newsgroups: comp.unix.i386
Subject: physical block size > 512 bytes
Keywords: Exabyte, blocksize
Message-ID: <701@ssp11.idca.tds.philips.nl>
Date: 26 Mar 90 11:05:07 GMT
Organization: Philips Information Systems, Apeldoorn, The Netherlands
Lines: 20


Does anyone know how existing UNIX device drivers handle physical block
sizes that exceed 512 bytes? For example, Exabyte cartridges use a
block size of 1 kilobyte by default. Two approaches are possible in case
the I/O is not a multiple of the physical block size:

1. An I/O of 512 bytes is written as 1 physical block.

2. The driver uses blocking to combine 2 I/O's of 512 bytes into
   1 physical block.

Obviously, the different approaches lead to incompatibility e.g. when
labelit/volcopy is used.

Thanks in advance,

Martin Peters

Internet:	martin@idca.tds.philips.nl UUCP: ...!mcvax!philapd!martin
Tel:	+31 5543 3163	Fax: +31 5543 3488	Telex: 	36345 phl nl