For background, please read the thread "Fusion-io ioDrive", archived at http://archives.postgresql.org/pgsql-performance/2008-07/msg00010.php To recap, I tested an ioDrive versus a 6-disk RAID with pgbench on an ordinary PC. I now also have a 32GB Samsung SATA SSD, and I have tested it in the same machine with the same software and configuration. I tested it connected to the NVIDIA CK804 SATA controller on the motherboard, and as a pass-through disk on the Areca RAID controller, with write-back caching enabled. Service Time Percentile, millis R/W TPS R-O TPS 50th 80th 90th 95th RAID 182 673 18 32 42 64 Fusion 971 4792 8 9 10 11 SSD+NV 442 4399 12 18 36 43 SSD+Areca 252 5937 12 15 17 21 As you can see, there are tradeoffs. The motherboard's ports are substantially faster on the TPC-B type of workload. This little, cheap SSD achieves almost half the performance of the ioDrive (i.e. similar performance to a 50-disk SAS array.) The RAID controller does a better job on the read-only workload, surpassing the ioDrive by 20%. Strangely the RAID controller behaves badly on the TPC-B workload. It is faster than disk, but not by a lot, and it's much slower than the other flash configurations. The read/write benchmark did not vary when changing the number of clients between 1 and 8. I suspect this is some kind of problem with Areca's kernel driver or firmware. On the bright side, the Samsung+Areca configuration offers excellent service time distribution, comparable to that achieved by the ioDrive. Using the motherboard's SATA ports gave service times comparable to the disk RAID. The performance is respectable for a $400 device. You get about half the tps and half the capacity of the ioDrive, but for one fifth the price and in the much more convenient SATA form factor. Your faithful investigator, jwb
