I understand how offsite pool reclamation works, but it is not going to reclaim the entire storage pool unless you set your threshold shockingly low. Otherwise, it is only going to skim off the few highly reclaimable tapes. I have a lot of high quality tape drives, but not enough to re-collocate an entire offsite storage pool on even a weekly basis. Our disaster recovery plan is...multilayered...like an onion...or an ogre. TSM is a part of it, but not the first line of defense. (If our policy was loose enough to allow us to wait until copy pool tape were full to send them offsite, then it would make more sense, but our average is about 40% utilized. We are required to send off tapes every workday. Many tapes are so underutilized that they reclaim in a day or two.)
Collocation does reduce tape contention between nodes and overall tape mounts during a disaster. If TSM is your only disaster recovery tool, and your environment is small enough it is be a great idea, no argument. But I just completed running Move NodeData on the primary pool of a department that no longer actively backs up. It took 2 months, running two or three nodes at a time. -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ads...@vm.marist.edu] On Behalf Of David E Ehresman Sent: Tuesday, November 24, 2009 11:35 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] collocation increases tape mounts while backup >>I am not sure if collocating a copy pool is beneficial. It seems like >>the copy pool as a disaster recovery pool would be ideal to collocate, but if you send off tapes every day you end up with a fragmented set of tapes for each collocation unit anyway. To clean that up would require bringing offsite tapes back onsite, exposing you to risk. It is possible to do a Move Nodedata in a copy pool, but the tapes have to be onsite. Perhaps there are better ways. << Collocating a copy pool is VERY beneficial, if you can afford it (and I might argue, you can't afford not to). You CAN reclaim a offsite copy pool; TSM uses onsite primary pool tapes to recreate the copy pool tapes that are being reclaimed. Collocating a copy pool does mean more tapes, more offsite tape movement, and more reclamation. But if the purpose of your copy pool is to allow you to continue business after a disaster, then you most likely will be under pressure to restore as quckly as possible and a collocated copy pool will certainly make those restores run faster. David Ehresman University of Louisville IMPORTANT: E-mail sent through the Internet is not secure. Legg Mason therefore recommends that you do not send any confidential or sensitive information to us via electronic mail, including social security numbers, account numbers, or personal identification numbers. Delivery, and or timely delivery of Internet mail is not guaranteed. Legg Mason therefore recommends that you do not send time sensitive or action-oriented messages to us via electronic mail. This message is intended for the addressee only and may contain privileged or confidential information. Unless you are the intended recipient, you may not use, copy or disclose to anyone any information contained in this message. If you have received this message in error, please notify the author by replying to this message and then kindly delete the message. Thank you.
