Re: Typical RAID5 transfer speeds

[Andre Tomt <andre@tomt.net>]

On 20.12.2009 10:55, Thomas Fjellstrom wrote:
> While the driver support isn't "perfect"*, I have an AOC-SASLP-MV8, a 2 port
> SAS 4x PCI-e card. (with SAS->SATA converters, its an 8 port SATA card)
>
> When I was running some tests on individual drives, and watching iostat, I
> saw over 500MB/s combined throughput, and that was with only 5 drives.
> Theoretically it should be capable of 1GB/s given its a x4 card.
> Theoretically.
>
> At the very least, the card should be more than capable of providing enough
> bandwidth for all 8 ports to be filled with regular mechanical hard drives
> (sans port expanders).

Having tried it connected directly to the north bridge, it seems to top 
out at ~650-700MB/s (also using Windows driver). Which is not too bad 
for a pcie 1.0 x4 card, but unfortunatly will only manage to saturate 
about ~5 modern mechanical drives (currently at 120-130MB/s each for 
SATA 7200rpm), if high sequential performance is all you're looking for.

Currently I solved that by having 4 drives from the array on that card, 
and populating the last four ports with with drives that are seldomly 
used and when used get mostly random i/o but still needs a port ;-)

Still good value for money, indeed.