"Scott Chapman" <[email protected]> wrote in message news:<[email protected]>... > We're just finishing up migration from a B20 Peer to Peer solution to a 7720-7720-7740 three-way grid solution. Performance has been much better, no surprise there. I'd say we've been pretty happy, but we're currently tracking down a cache management issue that cropped up with one of the 7720s when we lost the data links between the sites. It may be working correctly, we just don't understand it yet. >
I don't know what your cache 'issue' was, but I think this is explainable, the logical volumes that must be replicated to other clusters, are kept in cache. Depending on the size of your cache and the rate you generate tape data, this can fill cache to a certain threshold. You can check this in the GUI, in the "Pending Updates" view. When we bought the 7720, we could only get it with maximum cache (6 TB), but later smaller caches became available, which will fill up faster of course. > I'm not doing the migration work myself, so I can't really comment in detail, but my understanding is that Tivoli Tape Optimizer was problematic until we found the right combination of settings to get it to work smoothly. Actually, I think there was a bug that IBM provided a work-around or fix for. Just be sure to leave yourself adequate time to do the migration, it might take longer than you expect: the heavy read workload we're pushing through the B20 is causing our (8 year old) B20 to drop a drive or two a day. The CE has been able to fix most of them, but that takes time and we didn't really think about having to regularly run with less than the full complement of drives when planning out the migration. > We used CA's Copycat, which did the job very well. > > And don't trust a vendor's "average" compression ratio--go measure it out of your existing VTS for peak write times (it's in the SMF 94s for the VTCs). If you're (for example) backing up lots of DB2 data that's already compressed, that data is not going to compress well in the VTS. Assuming too high of a compression ratio and hence buying too little capacity could become a significant issue if you're in a disk-only solution. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ******************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ******************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
