Of speeds and feeds …

Kash posted the following as a reply to a Tom Treadway post. Since out of respect I won’t continue Tom’s posts I’ve made a new post in regard to this …

I took 7 SATA 300 drives of varying sizes (2 x 640GB, 4 x 500GB, 1 x 1TB) from different manufactures (WD 640, Samsung 640, Maxtor 500, 3 x Seagate 500, and I can?t remember the 1TB). In a Linux 2.6.29 machine with 2 x Intel QX9775s @ 3.0GHz, 8GB of RAM (4 x 2GB @ 1066) and an Intel DX5400 motherboard, I set up an LVM stripe over all of these devices. It didn?t allow the full size to be used (it defaulted to 7 x 500GB drives), but when I benchmarked the array, it saturated the PCI-E 2.0 bus. Yes. The drives pushed out 500MB/s constantly. I?m sure if I had PCI-E 3.0 (not out yet) it would have seen even higher speeds, considering that each drive (save for the Maxtor 500) pushes about 110-120MB/s on its own.

Kash … I need a lot more information before going to much further with this one. Firstly, need to know what card you are using. Since the PCIe specification doesn’t have a 500MB/sec limit - it jumps straight from 256 for x1 to 1GB/sec for x4, I’m not sure I see where your limitation is.

Since most of our cards are PCIe x8 they have a realistic throughput of 1800MB/sec (give or take a few mb). What sort of benchmark you are using, and whether it’s streaming reads or writes or random reads or writes will have a major impact on performance.

We have customers attaining well over 1000Mb/sec streaming read speeds from SATA drives these days, so there’s plenty of performance left for you to go yet.

Ciao
Neil