Yes, the disk space is still in use until you reuse the tape. This is the same as a tape library. Technically the rest of a tape is in use until you start writing to it from the beginning. Then the rest of the space on the tape is not used.
Say you've got a 100-slot library with 1 TB tapes. That's 100 TB of disk. Say you fill them all up, then expire 20 of them out of NBU, but do not relabel them. In NBU, the library now shows it's 20% free, but the VTL doesn't know that. But NBU does. If it needs a tape, it puts one of them in a virtual drive and starts using it. The second that happens the rest of the space on the tape is reclaimed. This is because NBU starts writing to the front of the tape, causing the VTL to say "oh!" I'm supposed to delete the rest of the blocks. Does that help? --- W. Curtis Preston Backup Blog @ www.backupcentral.com VP Data Protection, GlassHouse Technologies ________________________________ From: Clem Kruger [mailto:[EMAIL PROTECTED] Sent: Sunday, September 23, 2007 1:18 PM To: Liddle, Stuart; Curtis Preston; VERITAS-BU@mailman.eng.auburn.edu Subject: RE: Re: [Veritas-bu] Script to label expired tapes in a VTL Hi Stuart, In my experience we had to as the "DISK SPACE" was still in use! Kind Regards, Clem Kruger ________________________________ From: Liddle, Stuart [mailto:[EMAIL PROTECTED] Sent: 22 September 2007 21:35 PM To: Clem Kruger; Curtis Preston; VERITAS-BU@mailman.eng.auburn.edu Subject: RE: Re: [Veritas-bu] Script to label expired tapes in a VTL Clem, You have made a rather curious comment. You don't have to delete the tape to get the space returned. (My experience is with the NetApp VTL.) There are settings on the VTL that you can set to allow for how long you keep a virtual tape in the "shadow" pool once it has been "cloned" to physical tape. If you are not cloning to physical tape and are just keeping images on virtual tape, then you would not be "deleting" the tapes, you would be expiring images...just like Curtis said about the DSU. That's one of the nice features of the NetApp VTL. If you have the disk space, as long as you have cloned to physical tape it will keep the virtual tapes around until the VTL needs to free up space for newer backups. It does this for you automatically! --stuart ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Clem Kruger Sent: Saturday, September 22, 2007 2:33 AM To: Curtis Preston; VERITAS-BU@mailman.eng.auburn.edu Subject: Re: [Veritas-bu] Script to label expired tapes in a VTL Hi Curtis, You have to delete the tape to get your space returned. This is the real pain and cost Clem. -----Original Message----- From: Curtis Preston [mailto:[EMAIL PROTECTED] <mailto:%5bmailto:[EMAIL PROTECTED]> Sent: 22 September 2007 11:15 AM To: Clem Kruger; VERITAS-BU@mailman.eng.auburn.edu Subject: RE: [Veritas-bu] Script to label expired tapes in a VTL And you don't get the space back on a DSU until you expire the image. So what? I also argue that what Steve is asking for isn't necessary. (I think he's MAKING it necessary by oversubscribing, but that's not the VTL's fault.) Oversubscription aside, once his tapes are expired, the space taken up by those tapes is immediately available for reuse. The next time the tape gets written to, it will delete all pointers to the space taken up by that tape. As to the VTL vs disk debate, I still think you should bring in all disk devices and let them duke it out before excluding an entire category of them. You're going to exclude a lot of really good products if you just "no VTLs." Remember that saying "I don't want a VTL but I do want de-dupe" means that you're going to use NAS. While that will meet a whole lot of needs for a whole lot of people, there's also some really big backups that need a lot more than you can push over IP. For those backups, you're going to want a block transfer protocol (i.e. SCSI), and for that, you're currently going to be buying a VTL. (Unless you're just going to buy a non-deduped disk in which case I'd say you're REALLY wasting your money.) --- W. Curtis Preston Backup Blog @ www.backupcentral.com VP Data Protection, GlassHouse Technologies -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Clem Kruger Sent: Saturday, September 22, 2007 4:24 AM To: VERITAS-BU@mailman.eng.auburn.edu Subject: Re: [Veritas-bu] Script to label expired tapes in a VTL Hi Steve, This is the downer on VTL's. You do not get your "tape" space back automatically. It is for these reasons I recommend that one never go VTL's. NetBackup 6.0 and 6.5 allow disk to disk backups; the images are easily replicated to an offsite facility. The time for all "tape" has come and gone. The de-duplication facility in 6.5 makes life even easier. Why VTL's (which does SCSI emulation) when you and use disk which is faster and has more protection? Clem. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of swaltner Sent: 21 September 2007 17:32 PM To: VERITAS-BU@mailman.eng.auburn.edu Subject: [Veritas-bu] Script to label expired tapes in a VTL We deployed a VTL last month, which has been working very nicely. This is in a NetBackup 5.1 environment with the VTL attached to our Solaris based master server as well as to our NAS server for local NDMP backups. One thing I'd like to do is over-subscribe on the back-end storage, but before I do that I'd like to automate the process of freeing up the disk space used in the VTL when a NetBackup tape is expired. Just curious if anyone has already written such a beast and would like to share with me as a starting point. If not, I suspect I'll use the following logic: - Every day (at noon??), query the robots defined in the VTL and keep a record of tapes that are allocated. - When a tape goes from allocated to non-allocated from one day to the next, use a command like the following to erase the tape's contents: bplabel -erase -o -d dlt -m VTL123 This would write a small label at the beginning of the virtual tape, causing the VTL to drop all the other data that had been stored on the tape. Any reason this wouldn't work? Any gotchas with writing this script that I should look out for? Steve +---------------------------------------------------------------------- |This was sent by [EMAIL PROTECTED] via Backup Central. |Forward SPAM to [EMAIL PROTECTED] +---------------------------------------------------------------------- _______________________________________________ Veritas-bu maillist - Veritas-bu@mailman.eng.auburn.edu http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu _______________________________________________ Veritas-bu maillist - Veritas-bu@mailman.eng.auburn.edu http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
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