On Thu, 2006-09-14 at 16:35, Craig A. James wrote: > Alan Hodgson wrote: > > On Thursday 14 September 2006 11:05, "Craig A. James" > > <cjames@xxxxxxxxxxxxxxxx> wrote: > >> I'm experiment with RAID, looking for an inexpensive way to boost > >> performance. I bought 4 Seagate 7200.9 120 GB SATA drives and two SIIG > >> dual-port SATA cards. (NB: I don't plan to run RAID 0 in production, > >> probably RAID 10, so no need to comment on the failure rate of RAID 0.) > >> > > > > Are those PCI cards? If yes, it's just a bus bandwidth limit. > > Ok, that makes sense. > > One SATA disk = 52 MB/sec > 4-disk RAID0 = 106 MB/sec > > PCI at 33 MHz x 32 bits (4 bytes) = 132 MB/sec. > > I guess getting to 80% of the theoretical speed is as much as I should expect. Note that many mid to high end motherboards have multiple PCI busses / channels, and you could put a card in each one and get > 132MByte/sec on them. But for a database, sequential throughput is almost never the real problem. It's usually random access that counts, and for that a RAID 10 is a pretty good choice.
