It won't work. I tried and failed in a StorageTek SL500 library with
LTO4 and LTO5. Just like you are reporting, the LTO4 tapes would get
mounted in the LTO5 drives first, and then there was no free drive in
which to mount a LTO5 tape. I tried all kinds of tricks to make it work,
but it did not work.

Furthermore, despite claims of compatibility, I found that there was a
much higher media error rate when using LTO4 tapes in LTO5 drives,
compared to using the same LTO4 tapes in LTO4 drives. These were HP
drives.

The only way around it is to define two libraries in TSM, one consisting
of the LTO5 drives and tapes, and the other consisting of the LTO6
drives and tapes. Hopefully your LTO5 and LTO6 tapes can be identified
by unique sequences of volsers, e.g. L50001 versus L60001, which will
greatly simplify TSM CHECKIN commands, because then you can use ranges
instead of specifying lists of individual volsers. To check tapes into
that mixed-media library I use something like VOLRANGE=L50000,L59999 on
the CHECKIN and LABEL commands to make sure the right tapes get checked
into the right TSM Library. Fortunately the different generations of
tape cartridges are different colors.

You can read all about what I went through, and the good, helpful
recommendations from others on this list, by searching the ADSM-L
archives for "UN-mixing LTO-4 and LTO-5". Thanks again to Remco Post
and Wanda Prather for their help back then in 2012!

Roger Deschner      University of Illinois at Chicago     rogerd AT uic DOT edu
======I have not lost my mind -- it is backed up on tape somewhere.=====


On Wed, 10 Dec 2014, Grant Street wrote:

>On 10/12/14 02:40, Skylar Thompson wrote:
>> Hi folks,
>>
>> We have two TSM 6.3.4.300 servers connected to a STK SL3000 with 8x LTO5
>> drives, and 8x LTO6 drives. One of the TSM servers is the library manager,
>> and the other is a client. I'm seeing odd behavior when the client requests
>> mounts from the server. My understanding is that a mount request for a
>> volume will be placed preferentially in the least-capable drive for that
>> volume; that is, a LTO5 volume mounted for write will be placed in a LTO5
>> drive if it's available, and in a LTO6 drive if no LTO5 drives are
>> available.
>>
>> What I'm seeing is that LTO5 volumes are ending up in LTO6 drives first,
>> even with no LTO5 drives in use at all. I've verified that all the LTO5
>> drives and paths are online for both servers.
>>
>> I haven't played with MOUNTLIMIT yet, but I don't think it'll do any good
>> since I think that still depends on the mounts ending up in the
>> least-capable drives first.
>>
>> Any thoughts?
>>
>> --
>> -- Skylar Thompson (skylar2 AT u.washington DOT edu)
>> -- Genome Sciences Department, System Administrator
>> -- Foege Building S046, (206)-685-7354
>> -- University of Washington School of Medicine
>might be a stab in the dark ..... try numbering the drives such that the
>LTO5's are first in the drive list or vice versa.
>That way when tsm "scans" for an available drive it will always try the
>LTO5's first.
>
>HTH
>
>Grant
>