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What speed do you actually get with a PCI SATA II controller

Last response: in Systems
March 2, 2010 1:02:37 AM

Hello, I am wondering what speed would I actually get if I installed a PCI SATA II controller card in my computer to set up a RAID-O system. Would I get the 3 Gb/s transfer rate that the SATA II puts out or would I get the 133Gb/s transfer rate that the PCI puts out.

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a b B Homebuilt system
March 2, 2010 1:53:21 AM

You can't exceed 133 MB/s.
a b B Homebuilt system
March 2, 2010 12:49:37 PM

Be aware, however, that almost all SATA drives (including SATA II) can't actually deliver the 3 Gb/s data transfer rate. That speed is the MAX transfer speed for data from the drive unit (really, from its buffers) to the PC mobo. The real limit, however, is how fast the data can be read from (or written to) the spinning disk inside, and that tend to average out less than 1.5 Gb/s, the max rating of the first version of SATA. That's not a lot different from the speed rating of the PCI bus, so it may not be much of a limit.

This argument does NOT apply to SSD units, of course, in which there is no spinning disk to limit the data rate. Those units are the ones that will really benefit from the new SATA 6 Gb/s standard.
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a b B Homebuilt system
March 2, 2010 3:27:58 PM

It's not an issue with a single hard disk, but in RAID with several hard disks, then the PCI bus will become the limiting factor. That's why PCI-X was used on servers.
a b B Homebuilt system
March 2, 2010 3:29:37 PM

^+1 good point for anyone heading in the RAID direction!
March 3, 2010 12:26:10 AM

Thank you very much! I guess I will save me some money and forget buying the SATA II controller board. My motherboard has the SATA 1.5 in it now but I was hoping that the PCI SATA II controller board would match up with the SATA II HD. So I would probably do better speed going with my Motherboard SATA 1.5 than going with the PCI board. I am thinking about Buying 2 hard drives WD SATA II 250 GB 7200rpm 16 mb Cach for my RAID-O setup. I will have to put a jumper to bring them down to the 1.5 speed.

Thanks again!