For what it is worth I'll provide my experience with installing a sata storage pool and some observations about potential issues.
Dell 2550, 1gb ram, 2 x 1ghz pentium cpus TSM server v5.2.3.2 Windows 2000 sp4 160gb local scsi disk 6.4tb (16 x 400gb) local sata array fiber attached IBM 3494 with 2 dedicated scsi attached 3590-e1a drives 600 IBM 3590J tapes about 4.6tb of TSM data stored in primary storage pools about 100gb compressed client data stored daily
Our 3494 was filling up and management did not want to spend the $ to upgrade to 3592 drives and media. We added a 6.4tb fiber attached sata array which has about 5.3tb usable when configured for raid5.
Clients backup daily to the local scsi diskpool and once a day we migrate that storage pool to the sata diskpool. The sata diskpool is defined to TSM as a sequential with maxscr=260, file size of 20gb, reusedelay=8 and migrdelay=33.
Once a day we migrate about 2% of the sata pool to the collocated tapepool and do sata file reclamation and tapepool reclamation.
We see 85 to 90gb per hour throughput when migrating from the scsi disk to the sata. Running two migration processes doesn't seem to increase the throughput so I suspect the interface or pci bus is pretty well maxed with one migration process.
Sata file reclamation runs about 100gb per hour.
Sata migration to tape throughput is dependent on the number of tape mounts and how much tape seek there is. Process displays indicate 10-20gb per hour is the norm for us. Tapepool reclamation can see as high as 60gb per hour.
Overall it was fairly easy to implement. As far as tape use relief we are able to keep about 4tb of data on the sata so we now have less than 100 tapes used in the 3494. Cost for the sata, interface, cable, etc. was about $15k. No comment yet on the reliability of this brand of sata.
The only real issue I see right now is the limited throughput when migrating from the sata to tape. The migration is done one sata volume at a time which causes some collocated tapes to be mounted multiple times to receive client data from multiple sata volumes. Unless I missed something, multiple concurrent migration processes are not allowed (migpr=2 is invalid) for the sata diskpool so I'm not sure how I could increase this migration throughput. Perhaps I could define the sata volumes larger which reduces the number of volumes to be migrated and results in fewer potential multiple mounts of the same tape, a minimal improvement at best.
Questions, comments, suggestions?
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Steve Bennett, (907) 465-5783 State of Alaska, Enterprise Technology Services, Technical Services Section
