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From: marr@cup.portal.com (scott andrew marr)
Newsgroups: comp.unix.ultrix
Subject: Reading from 8mm tape
Message-ID: <32074@cup.portal.com>
Date: 25 Jul 90 23:09:25 GMT
Distribution: usa
Organization: The Portal System (TM)
Lines: 22

I am have a project where it is necessary to read, as fast 
as possible, large amounts of data from 8mm tape, 
using a DECstation 3100.  The data is stored on the tape by 
a real time data aquistion processor in 1K blocks.

I have been able to open the device and read from it using the
standard UNIX system calls (open & read).  The problem is that I
can only read 1 block per call, and the cycle time between two
reads is around a second.  The data on the tape is hundreds of
megabytes long, so the operation is unreasonable.

Does anyone know of a way to get more than just one block per
read?  The only thing I've come across is using something called
a nbuf facility (via ioctl) that implements multiple buffers, 
but I'm not sure what that will do for me (or to me!).  Any 
suggestions would be appreciated.

____________________________________________________________________________
                                   |           marr@cup.portal.com
	Scott Marr                 |                   or
				   |   marr@decster1.msd.lmsc.lockheed.com
____________________________________________________________________________