With TSM, it doesn't really make sense to make two copies of a tape, since things are managed at the object level. Copy Pools are used instead.
-----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] Behalf Of Paul Zarnowski Sent: Tuesday, September 30, 2008 7:56 AM To: [email protected] Subject: Re: NBU user considering switch to TSM At 06:58 PM 9/29/2008, steve sorenson wrote: > >> 1. He could make simultaneous copies during the initial backup, but not > >> during migration and while copying to the copy pool. > >> > > > > TSM can migrate from random-access disk to serial (tape), simultaneously > > copying to the copy pool(s). I don't have first-hand experience with this, > > but plan to soon. > > >I was referring to the feature of creating two copies of one set of data >simultaneously. NBU calls this Inline Tape Copy, where NBU takes one backup >stream and "twins" it, sending one stream to one device and another stream >to another device. It can do this either during the initial backup, or when >copying backups after the backup is done, like when you're migrating data or >making copies to go offsite. The point is to read the data and transfer it >in memory only one time, but have two copies when you're done. I was told >that TSM had a similar feature, but that it could only do this during the >initial backup, not when copying data. Do I understand this feature >correctly? In TSM, generally you have a disk storage pool in front of tape. At least, this is always the way I've used it, as this enables more concurrent backup sessions and collocation on tape. With progressive incremental, I don't really see the need to write to two devices simultaneously as the backup data is coming in over the network from clients. The point is, if you want to ensure that you've always got tape-resident data on at least 2 different tape volumes, you can do that in TSM. If you want to be sure that your data is fully protected on disk, before it gets to tape, I suppose you could do that with a disk subsystem that implements synchronous mirroring of some sort. If you want to have the incoming data be resident on both disk and a tape synchronously, as it comes in, you can't do that. I'm not that familiar with NBU, but if it does not employ progressive incremental, perhaps the desire to only have the data in memory once is more important? -- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Services Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [EMAIL PROTECTED]
