Conrad Macina wrote:

An LTO-series drive will read and write its own generation of tapes and one
generation back. It will read two generations back. So an LTO-4 drive will
read and write LTO-3 media and will read LTO-2. It will not work at all with
LTO-1 media. That's in the LTO spec, and is borne out by my experience.

When you write to a one-generation-back tape you get none of the capacity
benefit. A 400 GB (native) LTO-3 tape will still hold 400 GB when written in
an LTO-4 drive. I haven't done any rigorous benchmarks, but it appears that
you get about 80% of the speed benefit.

You can't put a higher-generation tape into a lower-generation drive. It
will eject right away, sort of like a cleaning tape, only faster. And
without any benefit to the drive. And NetWorker and the library will become
very, very confused.

Conrad Macina
Pfizer, Inc.



On Fri, 30 Apr 2010 08:29:57 +0300, Yaron Zabary <yaron AT ARISTO.TAU.AC DOT 
IL> wrote:

  I had an LTO-2 library with some 400 LTO-2 cartridges. When I
replaced the library with an LTO-3 library (Overland NEO8000 with four
HP LTO-3 drives), I simply moved all 400 cartridges to the new library
and it just worked. Then, within a few years I replaced the LTO-2 media
with LTO-3 media and all worked with no apparent problem. Recently, when
the drives were upgraded to LTO-4, it just worked (I only had to remove
the last LTO-2 cartridges that were still in). Now I have LTO-4 drives
and most of the cartridges are still LTO-3. Naturally, I will start
replacing the media with LTO-4 as the need arises.

George Sinclair wrote:

Is it a problem to recycle older LTO-3 media in LTO-4 drives and label
these into the same tape pool? This is in an all LTO-4 drive tape library.

I've had no issues reading from LTO3 tapes in the LTO4 drives, and they
are supposed to be backward write compatible (haven't tried that yet),
but will NW span mixed tapes properly, assuming all drives are LTO4?

George

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