p55 mobo speed limitations

[anttir]

This is an older hardware but I'd still like to know for sure before upgrading.

I have a P55 mobo (ASUS p7p55d) with six SATA2 slots and four Samsung Spinpoint F3's connected. I'm testing their speed with Ubuntu as OS.

Anyone of them can transfer up to 130 MB/s on their own. If I create a software RAID-0 (mdraid) I should be able to drive it up to 520 MB/s. However this is not the case.

The sata ports seem to be somehow paired. With disk connected to both port0 and port1 their combined speed is only 190 MB/s. When connected to port0 and port2 their combined speed is 260 MB/s. I can put drives to port0, port2 and port4 and get 390 MB/s (hdparm -t). Adding the fourth in slots 1,3 or 5 I get upto 440 MB/s or using the SATA3 slot I get up to 470 MB/s.

DMI1.0 should be able to go up to 2 GB/s.

Does anyone know what is this bottleneck? I'd like to avoid this with the next mobo.

 

[Auric]

I recall wonderings about such pairing with the H55 due to the storge controller's seperate sub-listings in Windows Device Manager with Microsoft drivers. Does it affect sustained rates as well as burst?

 

[anttir]

I recall wonderings about such pairing with the H55 due to the storge controller's seperate sub-listings in Windows Device Manager with Microsoft drivers. Does it affect sustained rates as well as burst?

I can't test it now but I did my small benchmarks with hdparm -t (Linux).

Do you think X58 could be an answer, or how about Areca RAID card ?

 

[Auric]

Presumably such a hardware card would be better but of course they tend to be expensive (LSI OEM server pulls tend to be relatively cheap though). Have you checked Intel's mainboard/chipset documentation for RAID setup recommendations (maybe pairing is mentioned)? I don't see any mention with a quick look at the help for Rapid Storage Technology.