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From: karish@mindcraft.com (Chuck Karish)
Newsgroups: comp.unix.aix
Subject: Re: Tape blocksize for 8mm
Summary: 512 0r 1024
Message-ID: <667864172.6818@mindcraft.com>
Date: 1 Mar 91 21:49:29 GMT
References: <22985@hydra.gatech.EDU>
Organization: Mindcraft, Inc.
Lines: 34

In article <22985@hydra.gatech.EDU> scott@prism.gatech.EDU (Scott Holt) writes:
>We have a number of IBM 8mm drives, both internal an external, 
>connected to various RS 6000 systems. I have come across a 
>problem using backup with the devices. In particular, if the
>block size device attribue is set to 0 (indicating a variable 
>length block), tapes subsequently written with backup cannot be
>read.
>
>So, the query is
>
>1) Is backup broke?

Probably.

>2) Is setting blocksize to zero on the 8mm device a dumb idea?

It's impractical on the 8mm and 1/4" drives.  It's necessary, though,
on the 9348 9-track drive; that one won't support tar or cpio unless
the blocksize is set to zero.

>3) Where might the legal attribute values for particular devices
>   be documented?

I don't know where they're documented, but the block sizes that work
are 512 and 1024.  There seems to have been a change between
3002 and 3003.

I wish IBM would provide a utility that knows how to make tape drives
work efficiently to be used as a filter between other utilities and the
drives, instead of building different partial knowledge of the drives
into different utilities.

	Chuck Karish		karish@mindcraft.com
	Mindcraft, Inc.		(415) 323-9000