If you collocate you run the risk of not being able to use the multi-session restore capability of the client. As for the n-servers backing up you will have N-files open...what if you're running a RESOURCEUTILIZATION higher than 2 on the client? You can have more that N files open if the clients have more than 1 data backup session running. On either collocation or not. You will just have to make sure your MOUNTLIMIT is set high enough on the device class.
As for the size, I would make it a managable number and a multiple of the filesystem size and pre-allocate the files using DSMFMT and define them to the stgpool. You could then define either a spacetrigger or a nextpool for your tape in case you run out of space. Pre-allocating the filesize let's you fill up the filesystem without having to figure out a MAXSCRATCH value. Should probably figure out what the "N" is above and allocate that many. Bill Boyer "Some days you're the bug, some days you're the windshield" - ?? -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Allen S. Rout Sent: Tuesday, December 06, 2005 10:46 AM To: [email protected] Subject: Re: Disk Only backups ==> On Mon, 5 Dec 2005 16:33:43 -0500, "Spearman, Wayne" <[EMAIL PROTECTED]> said: > We are planning to move a large number of our nodes to "disk only" > backups and eliminate tape for them. The diskpools will be > devtype=file. I struggle with whether to collocate these disk volumes > or not and how large to make them. I've had some discussions with IBM, > but would like to ask others to share their experiences with me. For collocation, my question would be 'Why ever not?' If you've got N machines backing up simultaneously, you'll have N files open; I'd say pick the "correct" N. As for size, My aesthetic opinion on this is that they should be substantially smaller than 1% of the enclosing capacity. So if you've got a 1TB of space, I think a 10GB volume is too big. The last time I actually picked a number, we had ~8TB of space, and I picked a 5GB volume size. This meant that my reclamation was happening in what felt like manageable chunks, and if I wanted to actually move things around I could do so on a sane granularity. The other force on volume size is "I don't want to have too many to manage". I'll assert that once you get into disk-only backups, you're going to have a volume count which you will -need- to manage in an automated fashion. So you _will_ be writing scripts to do things, instead of typing e.g. "move data" commands at the TSM> prompt. SO since you've already lost the manual-operation battle, you may as well go for the "reasonaby small" win. Keep in the back of your mind that backupsets are portable; if you write a backupset to disk, and then copy it somewhere else, you can use it indefinitely. So the FILE storage might be accessed from somewhere other than thru TSM. - Allen S. Rout
