Joni

Yes Reed is correct there.

This is only one of 3 problems, your raid configuration on your sata 
disks. the size of your TSM attrigates. or the placements of diskvolumes 
versus the accual phicial disks. for instance if you have more than 2 
volumes per phicial disk and you are doing backup on eatch volume you will 
hit a bottleneck on the I/O because of the head of the disk will be doing 
nothing more than jumping from one write operation to another. the same 
goes with read to tape. 
 



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Leigh Reed <L.Reed AT MDX.AC DOT UK> 
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
17.08.2005 16:17
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"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>


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Subject
Re: [ADSM-L] AW: [ADSM-L] Migration Speed Has Plummeted






Joni

I missed the URL off the last post, so firstly, here it is

http://www.redbooks.ibm.com/redbooks/pdfs/sg246638.pdf

I don't think that there is a maximum number of volumes that can be
configured in a primary storagepool with a devclass of disk and random.
We have 25 volumes that are 35GB each in size, for a total of 875GB. But
I must stress that this is on FastT disk which are FC.
I have seen postings where people have considerably more volumes
defined. However, as posts have said, the SATA disks are designed for
their 'sequential' nature and I believe that the more concurrent
reads/writes that you put through them, the performance degrades.

You say that you have 1TB of SATA disk, but you don't mention the
size/number of the disks.
For example, if the 1TB was comprised of 4 x 250GB drives, it may well
be worth only configuring 4 migration threads, to maximise the
sequential nature of the disks. Ie 1 disk sequentially writing to one
tape. Again, this is only theory, as I don't know that the internals of
TSM will function in this way.

Also, I haven't considered whether or not you have RAID'd the disks. You
mention that it is EMC disk and I assume that it is from the CX range.
It may well be worth speaking to EMC to ask if you can tune the
performance of the controllers for the type of I/O that TSM is doing.

Leigh

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Joni Moyer
Sent: 17 August 2005 16:23
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] AW: [ADSM-L] Migration Speed Has Plummeted

Hi Leigh,

I have brought in 1TB of SATA disk for random disk storage pools.  Would
you happen to know if there is a maximum number of volumes that can be
defined per storage pool?  If I have a disk pool that is 800GB, how many
volumes should I have defined?  What should the max. size of each volume
be?  If anyone has any ideas, please let me know.  Thanks!


********************************
Joni Moyer
Highmark
Storage Systems
Work:(717)302-6603
Fax:(717)302-5974
joni.moyer AT highmark DOT com
********************************



             "Leigh Reed"
             <L.Reed AT MDX.AC DOT UK
             >
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             Sent by: "ADSM:           ADSM-L AT VM.MARIST DOT EDU
             Dist Stor
cc
             Manager"
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Subject
             .EDU>                     Re: AW: [ADSM-L] Migration Speed
                                       Has Plummeted

             08/17/2005 10:39
             AM


             Please respond to
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Joni

The following URL is to the TSM V5.3 Technical Guide Redbook.

If you go to section 3.4.6, it discusses some changes in TSM 5.3 that
lend themselves to 'disk only backups'
Obviously, if you're not at 5.3 yet, then they may not be of use to you.

I personally would consider SATA disk as a possible replacement to
sequential tape, but I would still use good quality fast disk as
traditional 'random' disk pool to stage the nightly backups. I think
that it is widely recognised that significantly 'slicing up' the
diskpool into a large number of smallish volumes, greatly improves
performance (certainly on the backup). I believe that this is because of
the 'multi-threaded' nature of TSM.

I would imagine that the config for the best performance of SATA disk as
random TSM backuppool, would be to configure each SATA disk as a single
TSM volume within the backuppool and ensure that you have enough SATA
disks/backuppool volumes as you have sessions in at the same time.

However, with SATA disk capacity increasing rapidly, it's not efficient
to have a 100 x 250GB SATA disks (100 TSM volumes) sitting in your
backuppool, that only ever get 10% utilised.

I must state that this is just my opinion, I have no direct experience
with SATA disks.

Leigh