On Jul 31, 2007, at 11:59 PM, Stuart Lamble wrote:
I am not going to enter into a debate about the relative merits of raw volumes versus files on filesystems, as I have insufficient direct knowledge to judge either way (I'm trusting a more senior colleague to make the right call there. :)
I'll jump in anyway... The pure simplicity of RLVs makes them a joy to implement, compared to the time-consuming work entailed in implementing a TSM volume within a file system. Their simplicity almost makes them mandatory where rapid disaster recovery is vital, as there's far less TSM server set-up time getting in the way of recovering your organization's functionality. However, RLV access amounts to unbuffered I/O, and that exacts a performance penalty relative to file system volumes, where read-ahead provides a nice boost when the task at hand involves stepping through the volume. I use RLVs, and it's apparent that Migration is relatively sluggish, as in a disk storage pool struggling to stay empty enough to handle all the incoming client backup data so as to prevent some backups having to go directly to tape. The TSM Performance Tuning Guide cautions about this. Richard Sims, Sr. Systems Programmer at Boston University