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From: grog@lemis.de (Greg Lehey)
Organisation: LEMIS, Schellnhausen 2, 36325 Feldatal, Germany
Phone: +49-6637-919123
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Reply-To: grog@lemis.de (Greg Lehey)
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Subject: DDS-2 (was: I would like your comment on this configuration)
To: se@ZPR.Uni-Koeln.DE (Stefan Esser)
Date: Wed, 10 Jan 1996 16:36:01 +0100 (MET)
Cc: hackers@freebsd.org (FreeBSD Hackers)
In-Reply-To: <199601091616.AA10078@Sysiphos> from "Stefan Esser" at Jan 9, 96 05:16:13 pm
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Stefan Esser writes:
>
> On Jan 9, 17:20, didier@omnix.fr.org wrote:
>} Subject: I would like your comment on this configuration
>}
>} Mother Board:  ASUS P/I-P55TP4XE Rev 2.1 bios #401A0-0106 (Award)
>} Processor:     Pentium 133
>} Cache:         512k PB
>} Memory:        128Mb 60ns (DRAM)
>} SCSI:          Adaptec 2940W
>} Hard disks:    2 x Seagate Barracuda Fast Wide SCSI 2 Go
>} Video:         Miro 20SV  (S3-964, 2Mb VRAM)
>} DAT:           Conner 4326 4/8 Gb
>
> I'd definitely choose the HP1533A !
>
> It is some three times faster than the Conner,
> i.e. does 514KB/s (times compression factor).

I haven't tried the Conner, but I haven't got anything like that speed
out of a 1533A (especially considering that you appear to be using
normal DDS tapes).  But you (Didier) should be aware that the claim
4/8 GB is: (4: hope, occasionally seen; 8: blatant lie).  On those
tapes, with a normal mix, I get about 3.5 GB.

> Doing backups, I see some 800KB/s to 1100KB/s written to tape
> (depending on whether the data had been compressible or mostly
> compressed archives).
>
>
> Regarding DDS-2: I've heard multiple times, that DDS-2 tapes are not
> reliable. And since somebody had recorded nuclear physics data on
> DDS-2 tapes and had found no way to read back more than a few MB, I
> tried myself and now would never again trust 120m DDS-2 tapes.

I've been using a 1533A for several months now, and have had no
problems with the tapes.  You do need to keep the heads clean, though,
otherwise you'll see the problems you describe.  I make a daily backup
of about 7 GB, and read the tape back in daily just to be sure.

On the other hand, I *have* seen (and reported on) problems with the
SCSI tape driver.  I have the 1533A on a BSDI box, so I can't say how
FreeBSD reacts to that, but it doesn't like my old unmarked HP tapes
on the 35480A.

Greg