I can't speak for everybody's product out there, but the EMC CDL (EDL) releases the used pages from the virtual volume as soon as you begin to overwrite the virtual volume from the beginning. One thing that does this is a Label Libvolume.
It would be a simple script to look at all scratch tapes in the virtual library once a day, and issue a Label Libvolume on each scratch. Even in a large VTL this script would run quickly and have no impact on overall performance. Having said that, I personally don't think it is necessarily a wise thing to oversubscribe a VTL. By oversubscribe I mean to define, say, 150 virtual tapes when there would only be space for 100 virtual tapes if they were actually full. I had a customer do this once, and when the CDL became completely full TSM started getting I/O errors on all their virtual tapes, and everything went belly up, and there was no way to tell from a TSM perspective beforehand that they were getting close to full. If you are going to do this, you better set up CDL alerts and monitor the product, because TSM cannot help you monitor capacity. If you define 100 virtual tapes to a CDL that has 100 virtual tapes worth of capacity, then 'Q STGPOOL' will tell you how close to full the storage pool is, and be accurate about it. If you don't collocate this storage pool, then you ought to get virtual tapes completely filling up before you mount other virtual tapes, and thus get a fairly accurate picture of your resource consumption. Then if your reclamation is keeping up, you should be getting back scratch tapes often enough to keep up with demand. If you see the number of virtual scratch tapes deminishing over time, you are either not reclaming agressively enough, or you are outgrowing the CDL capacity and need to upgrade. Best Regards, John D. Schneider Sr. System Administrator - Storage Sisters of Mercy Health System 3637 South Geyer Road St. Louis, MO. 63127 Email: [EMAIL PROTECTED] Office: 314-364-3150, Cell: 314-486-2359 -----Original Message----- From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of Richard Rhodes Sent: Tuesday, June 12, 2007 10:11 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] How to Incorporate a CDL into a TSM environment? "ADSM: Dist Stor Manager" <ADSM-L@VM.MARIST.EDU> wrote on 06/12/2007 09:30:58 AM: > >> On Mon, 11 Jun 2007 23:50:20 +0100, Neil Schofield <[EMAIL PROTECTED]> said: > > > - Since the conversion of a pending delete volume to a scratch tape takes > > place purely in the TSM database, a virtual scratch tape will also occupy > > the full disk space on the VTL. until it is re-used. When DataDomain was in for a dog_and_pony_show the other day I asked about this. They claimed to be working with IBM to become application aware, so that they could release internal VTL storage when a tape goes scratch. I can see how this could be done, but I'll believe it when I see it. Rick ----------------------------------------- The information contained in this message is intended only for the personal and confidential use of the recipient(s) named above. If the reader of this message is not the intended recipient or an agent responsible for delivering it to the intended recipient, you are hereby notified that you have received this document in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. If you have received this communication in error, please notify us immediately, and delete the original message.