There is no absolute "right" answer to your question, except "it depends on
your environment".
We are also TSM 4.1.3 on AIX 4.3.3. There is no size limit I know of to the
files that TSM uses for DB, log, and storage pool volumes; you can make them
larger than 2 GB. However, the JFS filesystem where you are defining the
files must have the "large file enabled" attribute, otherwise AIX will not
let you create a file larger than 2 GB.
The number of files you use for the DB is mostly a performance/throughput
issue. TSM will start multiple I/O's to your DB (and storage pool) volumes.
So it is better to have multiple files than one big file, so TSM can do
multiple operations in parallel.
However, if you have MANY files, and they are all on the same PHYSICAL disk
volumes, eventually you will actually SLOW DOWN performance because you are
causing contention at the physical device level trying to do too many I/Os
to a single device.
So I try to think of it in terms of "how many concurrent operations do I
want to occur on that device?". But even that issue gets fuzzy if you are
using high-end RAID with CACHE in the controller, as much of the I/O becomes
asynchronous and is done to cache instead of being dependent on the physical
device rotation any more. So, "it depends" on your environment.
For example:
One of my TSM servers has about 400 clients, it is VERY busy and does
enormous amounts of I/O; I try to watch AIX iostat sometimes and just see
how much I/O is occuring to each of my physical drives, and how much time
TSM is spending on I/O wait, and I think in those terms when I'm putting new
TSM volumes in use.
My other TSM server is NOT a very busy server, and backup throughput is just
not an issue. On that system, I don't think twice about where I put the
files, or how many - it just doesn't matter!
Hope that helps provide some perspective...
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Wanda Prather
The Johns Hopkins Applied Physics Lab
443-778-8769
wanda_prather AT jhuapl DOT edu
"Intelligence has much less practical application than you'd think" -
Scott Adams/Dilbert
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