[ On Thu, April 2, 1998 at 00:02:31 (-0800), Alistair Crooks wrote: ]
> Subject: Re: Tape streaming 
>
> > > I have a 133MHz Pentium system with an AHA-2940, a Fast SCSI disk and an
> > > antique Archive Viper 2150S tape drive. If I do a level 0 dump of a
> > > filesystem from the disk to a tape, it won't stream continuously for
> > > more than a few seconds. I've tried winding up dump's "b" parameter to
> > > 700-800 with no obvious effect. This is with NetBSD 1.2 or 1.3.
> > 
> > I'd try piping the data through "buffer" (an old version of which is in
> > the packages collection) between the dump process and the tape device. 
> 
> Or try team, which is also in the packages collection.

I think you're all missing the point.  The 'team' and 'buffer' packages,
as well as other such double buffering tools, are wonderful in what they
do, but they really shouldn't be necessary in many circumstances.

Why can't a 133MHz Pentium with a fast disk and controller keep up to a
creeping old 2150S?  Heck my ancient Sun 3/260 could often do so even
with much slower disks.  Of course it was running SunOS-4 (which has
highly tuned SCSI drivers), and I was careful to use the dump 'c' option
(to specify cartridge tape params).

I just managed to get my 3/60 diskless workstation to stream to the
QIC-150 drive sitting on top of my monitor (mind you I had to first
cause NFS to cache the files locally, and I was writing rather large
files using 'tar -c -b 126 -f /dev/rst1 .' too, and I'm still running
SunOS-4 on it).

Perhaps the original poster wasn't using the largest possible buffer
size?  Since I have a Sparc-1 running NetBSD-1.3.1 running beside me
that I can plug the QIC-150 right into....  Yes, it can stream with
'dump 0cf /dev/rst0 /dev/rsd0g' (though there's a pause during during
directory writes, and another between directory writes and regular file
writes.  This machine has an ancient Maxtor 7120SCS drive in it.

Dump claims to be writing at 90 KB/s, which I think is about right for
SCSI versions of the QIC-150, esp. if you factor in serpentine
turn-around time, etc.

Hmmm..... even without '-c' it still streams A-OK.

Dump's '-c' option still seems to be for <30MB tapes though (at least on
SunOS-4 it defaults for 60MB tapes), and even without '-c' it wants 1.49
tapes to write 58098 blocks!!!!  It still doesn't have the write-to-eot
feature that FreeBSD has either!

-- 
							Greg A. Woods

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