Date: Mon, 23 Dec 1996 07:25:05 +0100 (MET) From: grog@lemis.de To: se@freebsd.org (Stefan Esser) Cc: freebsd-hardware@freebsd.org (FreeBSD hardware Users), aat81@pop.dial.pipex.com Subject: Re: your mail Message-ID: <199612230625.HAA03495@freebie.lemis.de> In-Reply-To: <Mutt.19961222213404.se@x14.mi.uni-koeln.de> from Stefan Esser at "Dec 22, 96 09:34:04 pm"
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Stefan Esser writes:
> On Dec 22, grog@lemis.de wrote:
>>>> Warning: Quality control on these drives varies greatly. One FreeBSD
>>>> core-team member has returned 2 of these drives. Neither lasted more than
>>>> 5 months.
>>
>> Well, this sounds very much like a report from me. But two things
>> don't fit:
>>
>> 1. I'm not a Core Team member.
>>
>> 2. I was talking about 37480As. These are an older version of DDS-1
>> drive. I do have a C1533A, and so far I've had no trouble with it
>> (more than 6 months, anyway :-) I think, in fact, I've had it
>> about 15 months, and I do a nightly backup which usually fills a
>> tape.
>
> Simon had previously sent mail directly to my address, and
> I told him to ask you and RGrimes for your experiences.
I'm assuming that, since you're writing in English, and WRT what you
say below, you'd like me to copy -hardware on this one, so I'm doing
so.
> He really wasn't that clear about what didn't work for him,
> and it may be something silly like using audio grade tapes,
> which can't be written to (unless some DIP switch is set to
> a non-default position, which might have been the case for
> his HP drive).
Yes, that's correct. It was one of the problems I was thinking of,
too. Let's wait for his reply.
>> I tried a Sony a long time ago. I think it was a 3000 or a 4000, and
>> they gave it to me in exchange for one of the broken 37480As. It
>> seemed to work OK, but it didn't have hardware compression, so I
>> returned it (couldn't read the old tapes written with the HP).
>
> The Sony SDT 7000 is even faster than the HP C1533A, which is
> a 3x speed drive. The Sony is 5x speed, taking advantage of a
> head drum developed for DDS-3. (And in fact, Sony is the first
> to announce availability of a DDS-3 drive, the SDT 9000, with
> 24GB (compressed) capacity, ie. 12GB native.)
Now there's some interesting information. For some reason, they don't
mention this in the data sheets. While I'm on the subject, what do
you know about the Archive 4586 NP tape changer? I've just bought one
of these, and so far (not really far enough to know), I'm happy. I
will report.
>> That's definitely not the direction of my problem. Mine worked fine
>> initially and then gradually faded, getting more and more read/write
>> errors as time went on.
>
> Hmm, that seems to be a good reason to return a drive before
> the end of the warranty :)
>
> But the head drum is generally not covered by warranty, since
> its useful life is typically in the 1000 to 2000 hours range.
> (Some 1000 8GB (compressed) backups at full speed, or 300 at
> 33% of the nominal streaming data rate !!!)
This, again, is interesting information for a number of reasons:
1. I haven't seen any information that the drum isn't covered. Maybe
I just forgot it. Unfortunately, I can't find any warranty
information.
2. The time you quote is *horribly* short. How can this compare with
the documented MTBF. According to HP, the MTBF for the 35470A is
50,000 power-on hours, and the MTBF for the C1533A is 200,000
power-on hours. In each case, they're assuming a duty cycle of
12% (which I exceed), so the real MTBFs would be 6,000 operating
hours for the 35470A or 24,000 operating hours for the C1533A.
My backups typically write a whole tape and take about 8 hours per
day. Tonight's backup started at 9 pm and finished (after a
verification read) at 5:07. That's a 33% duty cycle, which would
have the 35470A die after about 2 years.
If we took your figures, they should die after about 4 to 8
months, which is pretty much my experience. The only thing is,
this is the first I have heard of the figures. There's nothing in
any documentation I've seen which suggests that the drum is a
high-wear component. Laser printer documentation does indicate
that the print drum requires frequent replacement, for example.
> I've read about the new high capacity QIC drives, which offer
> identical capacity and data rate as a DDS-2 DAT. Typical long
> term cost might be about the same (expencive cartridges versus
> short lived head drums) ...
Interesting possibility. The oldest component I still (sometimes) use
in my system is my old Tandberg TDC 3800, now about 5 years old, which
has never given me any trouble. The current TDC 4222 can apparently
store 2.5 GB (5 GB with hardware compression) on a DC9250 tape (which
costs DM 48 or $32). They also mention a 13 GB cartridge (DC13GB) for
DM 127 ($83), but it's not clear what it's supposed to fit into.
Also, I recently got a brochure on Digital Linear Tapes, which use
conventional head technology. They apparently store between 30 and 40
GB on a single tape, but the cost is high: wholesale prices are DM
3790 ($2500) for the 30 GB model (Quantum DLT2000XT), and DM 6690
($4500) for the 40GB model (DLT4000). The tapes are comparatively
affordable: from DM 66 ($44) for a 20 GB tape to DM 175 ($115) for a
40 GB tape.
> Please post your findings to the hardware list. We'd need a lot
> more information like this in a place, where it is easily found.
> The Linux How-To concept beats anything FreeBSD has in this area!
What's Linux? Seriously, can you give me a pointer to the How-To
stuff? Maybe we should think about copying?
> (But I do also lack the time, to do anything else about this,
> other than to complain :)
What? Why do you lack time? Everybody else has plenty :-)
Greg
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