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'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. 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
