Hmmm, In that case, wouldn't the disks show 100% busy in nmon? AIX doesn't know about the XIV back-end processing. And, we also see these pauses on other TSM servers that are connected to an SVC.
No, I really think that something in TSM is slowing us down... -- Gr., Remco On 30 sep. 2010, at 11:20, Lloyd Dieter <ldie...@rochester.rr.com> wrote: > 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 > > > --
