RAID Question
 

I have a Freeagent Pro 500g esata external hardrive, and am considering buying another for a RAID 0 setup. Unfortunately, I have only one PCI-X slot on my motherboard, and its being used by my graphics card. I am thinking of buying this controller (http://www.axiontech.com/prdt.php?item=79223&tab=0) which supports both PCI-X and PCI buses. My question is, if I use a normal PCI bus, what kind of data transfer speeds will I get? Im assuming that 3Gb/s is out of the question with the slower bus, but how much slower should I expect? Im hoping to get at least 1.5 per drive, but would like to know with more certainty before purchasing anything. Thanks in advance!

did I put this in the wrong board?

Hi Robert........
 

You seem to be specialising in totally unanswerable questions. I suggest one reason you're not getting a response is that no one would be daft enough to say what, exactly, the configuration you're talking about will do in the real world. I certainly won't.

The only way you're going to know for sure is trying it yourself. With the wealth of inponderables involved there is no other way - lest someone has the identical MoBo, Bios level, card, configuration etc, etc, etc. The chances of that are, erm, extremely remote.

CS

I didn't realize this question was so "gray". I guess I thought that a pci bus had a standard transfer rate like USB 2.0(480Mb/s), Firewire(400Mb/s), etc. I thought all else being equal, there would be at least a way to determine the max the pci bus would allow. Anyway, thanks for the response.... I guess.

Standard PCI dates from about 1993 and was a 32 bit wide bus (so 4 bytes wide) that operated at 32 Mhz for a peak throughput of only 132mega-bytes per second or 1,024 mega-bits per second. So even one SATA at 1.5 or 3.0 megabits per second would saturate it for a each burst. Now you see why the AGP slot (for graphics at 2x, 4x 8x or 16x that) or PCIe (a high speed twisted pair bus) had to replace it. Basic PCI is only good now for modems, net cards and sound boards.

Allright, that makes sense. Question: I have an eSATA controller card now for the pci bus that promises up to 1.5Mb/s for one drive. Will the pci really provide that? Judging by your previous response, it probably wont. Thanks!

Well, it couldn't take the full burst, so the drive would send a couple of blocks as the bus allows. The full average throughput of a modern 7200 rpm drive is about 35-40 megabytes per second (280-320 mega bits) whichever version of SATA is in use, so the burst speed is not really that important. SATA and eSATA is still definitely faster than USB2.0 or either firewire. Average maxiumum throughput is usually about a third of peak or theoretical capacity of any bus system due to "queueing effects". Thats why so called 100 megabit ethernet, which theoretically could to about 10 megabytes per second, actually yields about 3, if everything is working well.

We did some tests on SATA raid and cheap drives that you may find useful. It worked so well, we built two :-) These motherboards are selling for around $200 these days and have 3 hardware RAID chips onboard.

Great tests.....
confirms my (5 year old) commercial experience that RAID5 is great for random reads, its just I found that it is lousy for sequential writes.

Also interesting that despite SATA "command queueing", SCSI drives still excel at random ("scatter-gather") reads.

Still confirms SATA is very cost effective for video with its sequential reads and writes.

Can you give a little info on how you used this setup? Such as, whic drive held the captured files from camera, which you rendered out to, etc. Thanks!