As can be seen, the notion of multiple restore is complicated. I'm sure that the Tivoli engineers are working hard on implementation ideas. I hope that they have lots of people that have seen various environments and know what we see out here. Hint, hint, hint. Let's make sure we get a bunch of input before we write something that nobody can use!
Thanks, Kelly J. Lipp Storage Solutions Specialists, Inc. PO Box 51313 Colorado Springs, CO 80949 [EMAIL PROTECTED] or [EMAIL PROTECTED] www.storsol.com or www.storserver.com (719)531-5926 Fax: (240)539-7175 -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED]]On Behalf Of Robin Sharpe Sent: Thursday, December 20, 2001 8:02 AM To: [EMAIL PROTECTED] Subject: Re: Incremental forever -- any problems? (Scary thoughts) Oops ----- Forwarded by Robin Sharpe/WA/USR/SHG on 12/20/01 10:01 AM ----- Robin Sharpe 12/20/01 09:14 To: [EMAIL PROTECTED] AM cc: Subject: Re: Incremental forever -- any problems? (Scary thoughts)(Document link: Robin Sharpe) But wait a miniute.... doesn't the multi streamed backup work by allocating a session to each filespace (filsystem or disk partition)? I'm not sure you would get multiple streams if you are only backing up a single filespace. If that is true, then I would guess that Tivoli will implement a multi-stream restore in the same way -- one session for each filespace being restored. On the other hand, I don't think there is any technical reason why the backup couldn't split even a single directory between two sessions. But that's not true for restores (as you have all said already)... it will only work if the data is on multiple tapes. However, let's assume we have a non-collocated pool containing a client with a wide variety of data... 30% that rarely changes, 30% changes weekly, and 40% changes daily, and all of the data is on a single filespace. After several months of backups the active backup data will probably be spread over several tapes. We now need to restore that filespace due to a disk crash. A well-implemented multi-stream restore should be able to sort the data by tape volume and start a session for each volume. Note that we can't even do that manually now, because we have no way of knowing what tape contains what active versions. I think it's important for Tivoli to implement multi streaming in this way since so many NT clients have only one or two filespaces... In our shop, most have two -- a C: drive for NT and a D: drive for files or Notes or whatever. Robin Sharpe Berlex Labs Michael Bartl <michael.bart [EMAIL PROTECTED]> To: [EMAIL PROTECTED] cc: (bcc: Robin Sharpe/WA/USR/SHG) 12/20/01 Subject: 03:51 AM Re: Incremental forever -- any problems? (Scary thoughts) Please respond to michael.bartl Hi Kelly, your're right, a multistream restore is one of the items on top of our wishlist. Just one thought on collocation: With collocation you can't mount as many tapes as without, ok. But with collocation, data from one node is much more compactly written to one tape. So when you don't use collocation and you have to mount 50 instead of 7 tapes (or even 7 instead of one) you have to keep in mind that TSM has to skip 6/7 of the data on the tapes while reading them. So collocation would remain an important feature, the benefit just decreasing in size (compared to now). Best regards, Michael Kelly Lipp wrote: > > On the wishlist item: > > I have heard talk about implementing an automatic multi-stream restore > similar to what we have now with backup and resourceutilization. This will > be slick but then only really slick if one uses collocate=filespace. I > believe it will still provide better restore times since it will know what > tape volumes client data is on and will mount multiple volumes. If one > thinks about this for a few minutes, one realizes the whole thing is damn > complicated. Also, it would appear that collocation would not be a good > thing if you use this technique: you want data on multiple tapes. > -- Michael Bartl mailto:[EMAIL PROTECTED] Office of Technology, IT Germany/Austria Tel: +49-89-92699-806 Cable & Wireless Deutschland GmbH. Fax: +49-89-92699-302 Landsberger Str. 155, D-80687 Muenchen http://www.cw.com/de
