Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!att!lzaz!hcj
From: hcj@lzaz.ATT.COM (HC Johnson)
Newsgroups: comp.sys.amiga
Subject: Re: Stream tape backup
Message-ID: <623@lzaz.ATT.COM>
Date: 12 Jun 89 21:22:48 GMT
References: <120@snll-arpagw.UUCP> <17182@louie.udel.EDU> <1942@ektools.UUCP>
Organization: AT&T ISL Lincroft NJ USA
Lines: 39

In article <1942@ektools.UUCP>, barrett@ektools.UUCP (Chris Barrett) writes:
> >In article <120@snll-arpagw.UUCP> paolucci@snll-arpagw.UUCP (Sam Paolucci) writes:
> >>Does anybody know of a SCSI stream tape backup system that works on the
> >>Amiga?  
> >
> I have gotten my 60 Mb SCSI tape drive to work with the C.Ltd SCSI interface
> ...not very fast also, about 1.5 hours for 10 Mb, don't really know why yet, 

I've worked with a SCSI tape on both PC and ATARI.  In the default mode
this bugger writes one 512 byte block per request as the sequence:
write block
write a long blank space
backup
This take greater than a second, and it is S L O W!!

The trick(s) is to configure the tape unit into burst mode (part of the
config command) and then deliver at least 16 blocks of 512 at a time,
and don't waste much time between blocks.

for example, the unix command
find . -print | cpio -oc > tape  is VERY slow
find . -print | cpio -oc | dd of=tape obs=500b(locks) is fast.

I use this to get MINIX to play fast on the Atari.
On TOS (native to ST) it is possible to read the disk in 16 block chunks
in time to write to the tape and keep streaming.

Bottom line:

configure the tape to burst mode
either write large bursts infrequently, or
write bursts of 16 quickly,

and your streaming tape will make you happy.

Howard C. Johnson
ATT Bell Labs
att!lzaz!hcj
hcj@lzaz.att.com