I just migrated our TSM system to a new pSeries 6H1 from our old F50. While I/O throughput is much higher, the database performance is surprisingly poor. I am asking for help in trying to figure out why and what I can do about it.
TSM 4.1.5.0 running on AIX 4.3.3 ML 10 6H1 2-way 600 MHz 64-bit 4 GB RAM 27 GB TSM database with 256 MB DB buffer pool Four 4-drive libraries, each double-connected via SCSI (two drives per adapter) This system has been in service for one day. The same backup system had been running on the old F50 since ADSM 2. On our old F50, I had split the database into many 1 GB volumes as an experiment when we had only 512 MB in our TSM server. It didn't seem to hurt performance so I'd left it that way. When I built the new server, I took advantage of info on this forum and created a single large DB volume on each DB disk. The DB is currently laid out this way: SCSI Adapter #1 --> DB disk 1 (one vol) --> DB disk 3 (one vol) --> Log disk 1 (five vols) --> Pool disk 1 SCSI Adapter #2 --> DB disk 2 (one vol) --> DB disk 4 (one vol) --> Log disk 2 (five vols) --> Pool disk 2 DB and log volumes on odd-number disks are TSM mirrored to volumes on the even-number disks (the volume on DB disk 1 is TSM mirrored to the volume on DB disk 2 for example). Yesterday we saw decent performance during expiration and reclamation of two primary tape pools. When a third pool's reclamation started, and especially when the system had to handle reclamation of all three primary pools and the copy pool and client sessions, the overall performance was very poor. Watching system activity with topas showed overall disk I/O on the DB disks to be very low - much lower than we saw on the old F50. Oh... I know TSM 4.1 is not supported any more. This server upgrade was a prerequisite to the software upgrade which will occur in about a month or so. Also, I know I can set a larger DB buffer pool than 256 MB and will do so over the next couple/few days. But we had better database performance on the F50 with a DB buffer pool of only 128 MB. ==> So what should I do? Split the database into "a few" volumes? Or should I look elsewhere? Thanks in advance. Tab Trepagnier TSM Administrator Laitram LLC
