Agreed.

We have DLT7000's in STK9710's.  We have had no problems at all with the
robotics, or with the other types of drives and media we have in the 9710's.

But for 2 years we have had constant problems with the DLT7000's.  (People
on this list don't seem to report many problems with the 4000's, dunno the
difference.)

My experience also is that DLT does NOT stand up to lots of tape positioning
requests.  We have had to give up collocation on our storage pools because
each DLT cartridge got appended to many times in the course of a week with
collocation on, resulting in lots and lots of readback errors.   Without
collocation, each tape is appended to only once or twice before it fills and
we have many fewer readback failures.  But without collocation, our recovery
times for entire servers are so much longer that we are planning on giving
up DLT and replacing our drives.

Now the issue here is still one of perspective.  We have never actually lost
a significant amount of data due to DLT errors, because I keep multiple COPY
pools, and I can always get the data back from somewhere.  It just costs you
a lot of TIME if you can't restore a file off your primary pool tape.

If I had a choice between 4mm or 8mm and DLT, I would still recommend DLT.
You can store so much data on 1 cartridge, it can be cost-effective to use
DLT and just keep extra copies of the data to guarantee recoverability of
the data.

So it depends on where you are coming from, and what your expectations are.
Whether your primary concern is cost, or recovery time, or floorspace!
Getting something MORE reliable than DLT definitely requires more bucks,
costs more bucks per megabyte, and sometimes more floor space.    If you are
coming from a 4mm - 8mm environment, DLT is a step up, just remember to
account for it's capabilities in the way you set up your operations.  If you
are coming from a 3490/3590 environment, it's definitely NOT going to be as
robust.

My opinions entirely,

Wanda Prather





> -----Original Message-----
> From: David Boyes [SMTP:dboyes AT DIMENSION DOT NET]
> Sent: Thursday, August 05, 1999 9:31 AM
> To:   ADSM-L AT VM.MARIST DOT EDU
> Subject:      DLT reliability
>
> >But i'm interested in the reliability of DLT tapes. How many damaged
> >tapes have the members of this list seen in their live?
>
>
> Dozens. DLTs are high density, but very sensitive to environmentals.
> Temperature, pressure, humidity all have a serious impact on DLT
> performance and lifetime -- most small shops don't maintain a controlled
> environment that supports longterm DLT usage.  Drop one or knock it off a
> desk and the data's probably gone. They also hold up very poorly to lots
> of tape positioning requests (in a non-collocated environment, DLTs don't
> work well at all).
>
> In most "open systems" environments, I don't recommend using DLT
> cartridges for more than 4 months before replacing them.  If you look at
> the total lifecycle cost of using the DLTs, the 3590s start to look like a
> good idea very quickly.