Joni,

You gave the following estimations:

          3590  9840 9940A    LTO
         10 GB 20 GB 60 GB 100 GB
Production
Onsite    1375   689   231    140
Offsite   1600   800   268    161
Total     2975  1489   499    301

Test
Onsite     963   483   163    101
Offsite   1324   664   223    135
Total     2287  1147   386    236

Grand
Total     5262  2636   885    537

And IBM offered a 3-frame 3584. There are some things to consider with
these numbers.
1. Do you use collocation. For your onsite tapes you need at least 1 (often
2, 1 full and 1 filling) for every node or filespace you use collocation
for.
2. Reclamation. Reclaiming 20% of a 10Gb cartridge works very well, but
with 100Gb cartridges this becomes a very long process. We use 3590K
cartridges with E-drives (40Gb capacity) and is is very hard to get a good
tape occupancy. This is especially the case for our offsite tapes because
we sent them offsite every day and therefor they aren't filled up. When we
were using 3490 cartridges we used to reclaim at 50%, now we hardly ever go
below 80%.
3. Offsite cartridges. As I said above, it's very hard to fill offsite
cartriges to capacity. You have to look at your Backup Storagepool
processes. Do you have more than 1 primary storage pool and if so, do you
run Backup Storagepool in parallel or serially. How many Gigabytes do you
sent off daily.
4. Library capacity, with the above numbers 880 slots would be sufficient
because you only have 241 tapes onsite plus your scratch.

We are looking at the option of moving TSM from OS/390 with 3590 to AIX
with LTO. We are now using appx. 500 40Gb tapes and our estimation for LTO
100Gb at the moment is slightly less (say 400-450 tapes) because of the
above mentioned reasons.

All these arguments are valid to a lesser extent for 9940A and 9840. Just
realize that the higher the capacity the lower the usage (percentage wise).

Hope this helps,

Luuk Kleibrink
Delta Lloyd
Netherlands


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