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From: johnson@aixwiz.austin.ibm.com (Fred L. Johnson)
Newsgroups: comp.unix.aix
Subject: Re: 1/4" tape and record sizes
Message-ID: <8172@awdprime.UUCP>
Date: 4 Jun 91 19:13:09 GMT
References: <1991Jun3.024011.387@odi.com>
Sender: news@awdprime.UUCP
Reply-To: johnson@aixwiz.austin.ibm.com (Fred L. Johnson)
Organization: IBM
Lines: 38

In article <1991Jun3.024011.387@odi.com>, benson@odi.com (Benson I.
Margulies) writes:
|> From: benson@odi.com (Benson I. Margulies)
|> Subject: 1/4" tape and record sizes
|> Date: 3 Jun 91 02:40:11 GMT
|> 
|> My 320 has the usual IBM/tandberg 1/4 inch polymorphously perverse
|> tape drive. (anyone know where to get a drive like this that writes
|> both 60 and 150 MB for a sun?)
|> 
|> In smit, its configured for 512 byte blocks. I write tapes with backup
|> -i (for consumption of installp). tcopy, documented to report on
|> record sizes, swears that the tape blocks are 65536 bytes long.
|> I think it's lying. Can anyone convince me otherwise?
|> 
|> 
|> -- 
|> Benson I. Margulies

tcopy is telling you the size of the buffers that it used with its read system
calls.  I does not report the size of the physical blocks on the tape.

What you see in SMIT is the size of a physical block on the tape.  The actual
buffer sizes used with the read and write system calls need only be multiples
of the physical block size.  tcopy happens to use 65536 bytes.  backup by 
default uses 100 block (51200 byte) buffers for tapes.

- Fred

My remarks and opinions are mine alone...
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