Hi Team,
I?ve a question about mixing LTO drives and media in the same library ? LTOn
and LTOn+2.
? Windows TSM 5.4.3.2 (soon to be migrated to a 5.5.1.1 server running on
AIX)
? IBM 3584 single frame library, presently with 4 x IBM LTO2 drives
? Currently no library clients or storage agents.
My client is looking to migrate from 4 x LTO2 drives to 8 x LTO4 drives in
their 3584 library (as well as performing some other TSM Server platform
migration activities).
The LTO drive generation-spanning capabilities are such that LTO4 drives can
read from but not write to LTO2 media; that LTO2 drives can read/write to
LTO2 media, but will have nothing to do with LTO4 media.
Now, for an interim period, it has been suggested that the library be
configured with 5 x LTO4 drives and 3 x LTO2 drives. TSM Server and the IBM
3584 Tape Library are both stated to support mixed media and tape drives
between these LTO generations.
However, the idea behind this is that during this interim period, new
incoming backup data should be written to LTO4 media by the LTO4 drives (as
well as some existing LTO2 data being moved/consolidated onto LTO4 media),
and that offsite copies only continue to be generated to LTO2 media using
the LTO2 drives (various reasons for this, including maintaining media
compatibility for DR purposes). If possible, largely I think for
flexibility, the preference is to achieve this within a single library
partition.
It?s this last bit that I?m having trouble getting my head around.
Obviously, a new device class (FORMAT=ULTRIUM4C) will be added to the TSM
Server to make use of the LTO4 drives (making sure that the current LTO2
device class is locked down to FORMAT=ULTRIUM2C), as will a new set of LTO4
storage pools pointing to this new device class. However, with both of these
drive types being located in a single library partition I don?t quite see
how they?ll be able to make sure that only LTO2 scratch tapes get mounted
into LTO2 drives and that LTO4 drives don?t go trying to write to LTO2
media. Is it simply a case of manually allocating the LTO2 scratch media to
the LTO2 copy storagepool (and setting its MAXSCRATCH to 0), and ensuring
that LTO4 is the only media in the general scratch pool? Will TSM ensure
that, given we?re explicit in our device class definitions, when a backup
stgpool operation requests a mount of an LTO2 scratch volume (or indeed an
LTO2 filling volume) to perform a write it?ll only mount one into one of the
LTO2 drives, and similar for LTO4 media and drives? I suspect not...
Is anyone running with a similar configuration to this (if it?s possible)?
Of course, the other blindingly obvious option is to partition the 3584,
creating one library partition for the 3 x LTO2 drives and enough slots to
manage the offsite requirement, and another for the 5 x LTO4 drives with the
remainder of the carts. The client doesn?t have ALMS for quick flexible
library partitioning (I don?t know about the cost of this feature, but I
expect that they?d be unwilling to consider it for only an interim period)
so we?d have to use more rigid non-ALMS partitioning method. This option
appeals to me in that it?s pretty simple to get my head around, but perhaps
requires a little more work to perform the library repartitioning.
Any thoughts gratefully received!
Cheers,
David Mc,
London, UK
No virus found in this outgoing message.
Checked by AVG.
Version: 7.5.524 / Virus Database: 270.11.18/2009 - Release Date: 18/03/2009
07:17
|
