Just brainstorming here, Couldn't you create a copypool into the same DD device class? If you had 2 pools in the same DD device, it should hypothetically, dedupe down to the size of just one, since it is (by definition) identical data. Then you can replicate both pools to the other site with the internal DD replication. If there was a problem on the initial write of one of the copies, then the DD shouldn't deduplicate that. And this *shouldn't* cost anything except for the I/O of TSM creating the local copypool.
That said, DD has that "data invulnerability" feature which verifies the write after it hits the disk. I think it's industry acceptible at this point. Even the IBM/Diligent designs go with the single pool model, even though they don't have this post-write verification. Is corrupt data something that anyone sees on these VTL/Storage targets? We had a compression card failure in 2007 that caused corrupt data to be saved to disk (different vendor) The 2-pool model saved us that day. Ever since then, I've been hesitant on the one-pool model, although I haven't heard of any data corruption issues lately. I may be coming around. Regards, Shawn ________________________________________________ Shawn Drew Internet charles_h...@uhc.com Sent by: ADSM-L@VM.MARIST.EDU 03/22/2011 09:42 AM Please respond to ADSM-L@VM.MARIST.EDU To ADSM-L cc Subject Re: [ADSM-L] draining a diskpool when using a DD and no copypool We've run in to the same conundrum, do you let the device replicate the deduped data and create the situation described below or do you just let TSM handle the Offsite copy and end up transferring all the backups data from the prior night, this assumes you have adequate bandwidth to your remote site. We chose to let TSM do the copy as we have the bandwidth available like the fact of granular control over the VTape and Seq File volumes. Regards, Charles Hart -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ADSM-L@VM.MARIST.EDU] On Behalf Of Rick Adamson Sent: Tuesday, March 22, 2011 8:29 AM To: ADSM-L@VM.MARIST.EDU Subject: Re: [ADSM-L] draining a diskpool when using a DD and no copypool Rick, About a year ago we implemented the Data Domain system just as you described and after having some time to study its operation and design I would urge you to think long and hard about it and debate the design with DD and TSM Support. My concern is this, as recommended by Data Domain we removed all copy pools and replicate a duplicate copy of our entire primary sequential (file) storage to our DR site. The problem is; what do you do if you incur corruption or some other issue in the primary pool that would normally be resolved by marking the volume as destroyed and recovering the data from the copy pool (which is now non-existent). While I have not begun the discussion yet I think a better design approach may be to either use the DDR as a copy pool resource or incorporate the resources at the DR site to add copy pools. Think about it in terms of "what if" something happened to the data at the primary facility and it got replicated to the DR site, what would be your option to resolve? I don't see any. Feedback anyone? ~Rick Adamson Jacksonville, Fl. -----Original Message----- From: ADSM: Dist Stor Manager [mailto:ADSM-L@VM.MARIST.EDU] On Behalf Of Richard Rhodes Sent: Tuesday, March 22, 2011 9:13 AM To: ADSM-L@VM.MARIST.EDU Subject: [ADSM-L] draining a diskpool when using a DD and no copypool Hello everyone, An interesting problem . . . we are implementing a Data Domain system. It will be configured as a file device via NFS mount. DD replication of the primary file device pool to the DR site will be use so there will be no copypool. We will still use a diskpool with migration into the file device pool, and this brings up a problem. The majority of backups come in over night into diskpool and get migrated. But some backups (Oracle archive logs, long running backups from remote sites and some others) come in at any time around the clock. Since DR relies on DD replication of the primary file device pool, we MUST make sure that at some point every file in diskpool gets migrated. With ongoing backups coming into diskpool, migration to 0% may never complete. The one thought we had was to once a day (after migration completed) run movedata on each diskpool volume. We've asked DD this question, but so far they haven't provided an answer. Thanks! Rick ----------------------------------------- The information contained in this message is intended only for the personal and confidential use of the recipient(s) named above. 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