I did some restore tests previously and found with my multi-session restore
tests some of the restores were waiting for a long time for volumes that
were in use.  It was this that made me think that collocation was not good
for this.  At that point in time I was using 25 GB volumes, I've since
switched that to 4 GB volumes.

I just did a quick test - restoring 46.1 GB, 217,310 objects

With no collocation, the data was spread across 36 volumes.  With
collocation it was spread across 14 volumes.

No collocation restore and 8 mount points: 35.5 minutes, 22.2 MB/sec
With collocation and 1 mount point: 68.9 minutes, 11.4 MB/sec
With collocation and 8 mount points: 34.8 minutes 22.9 MB/sec

So in my case as long as the data is spread out among a number of volumes
(with collocation or not) multi-session restore works with a higher
throughput than single session restore.

So now I'm beginning to think that collocation may be good as long as the
volume size is fairly small.

My environment:
TSM Server 5.22 on Windows 2003
TSM Client 5.229 on Windows 2003
The volumes are defined on SCSI disks (not ATA)
Client compression is on

It would be interesting to see what other people are experiencing.

Thanks,

Tim Rushforth
City of Winnipeg
-----Original Message-----
From: Otto Schakenbos [mailto:otto.schakenbos AT TELEFLEX DOT COM]
Sent: August 2, 2004 8:15 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: D2D vs. tape backups with TSM?

Food for thought on multiple sessions and filebased backup:
If you got 2(or more) virt. tapes on one disk(array) and the client has
mounted them both and is pulling data from them this will probarly be
slower in throughput then when just reading from one virt. tape at a
time since sequantial reading is normally faster (esp. with ata) then
random.
In other words multiple mount points means the heads of your disk has to
move longer distances then when using a single mountpoint.
Thats why we have collocation turned on and only allow single sessions
on our file type backup pool.

maybe we are doing it all wrong anyway...

regards

Otto Schakenbos
System Administrator

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