For B20 if cache full, we will encounter a throttling write/read, is it still happen in 7720 model, or have enhancement on throttling read/write ?
2012/3/29 Vernooij, CP - SPLXM <[email protected]> > "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 > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
