I'm betting the pauses are the XIV destaging data from cache to physical disk.
Not a big fan of using heavily cached disk LUNs for disk/file storage pools.... On Wed, 29 Sep 2010 13:47:47 +0200 Remco Post <r.p...@plcs.nl> wrote: > Hi all, > > I'm currently testing TSM 5.5.4 on AIX 5.3 with an IBM XIV box. > > When I use dd or other tools to copy data off the disk to tape (LTO4), we > get quite a good performance, 100 MB/s or better. Even when backing up data > on the XIV via shared memory directly to tape, we're quite happy, we can > read the data at over 100 MB/s for one backup job, and for over 200 MB/s for > two jobs. But, when TSM uses the XIV for DISK volumes, we're not in a happy > place, backing up data from one XIV to TSM with diskpool on another XIV, we > get about 55 MB/s per backup job, best case. Both XIV boxes are otherwise > completely idle. When migrating data of the diskpool to tape, it's the same, > no matter what we do, we don't even get close to the LTO4 native > performance, about 70 MB/s is the best I've seen, and usually it's less. The > TSM server is at that time only running the migration, nothing else. > > The stragest thing we notice is that TSM seems to completely pause every so > often, no disk i/o, no tape i/o no cpu utilization, nothing for about one > second, and the it goes again. When I let two migration processes run, this > is less obvious, because one process continues while the other one pauses. > > We've opened a hardware call with IBM to find out if there are any settings > on the hdisks or HBAs that we need to change, and even though we did get > some hints, and some performance improvement out of that, we fell that TSM > should be able to do a lot better. > > Does anyone else have experience with XIV as a diskpool? and if so, what > sort of performance do you see? > > -- > Met vriendelijke groeten, > > Remco Post, PLCS --
