Yup, a separate channel for each drive plus having them all connected to a PCIex8 controller would make a big difference.<br><br><div class="gmail_quote">On Fri, May 20, 2011 at 4:54 PM, Trevor Cordes <span dir="ltr"><<a href="mailto:trevor@tecnopolis.ca">trevor@tecnopolis.ca</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">My RAID6 8x 2TB-drive SATA XFS gives:<br>
<br>
#dd if=/dev/zero of=/new/test bs=1M count=32768<br>
<div class="im">32768+0 records in<br>
32768+0 records out<br>
</div>34359738368 bytes (34 GB) copied, 152.032 s, 226 MB/s<br>
<br>
#dd of=/dev/null if=/new/test bs=1M<br>
<div class="im">32768+0 records in<br>
32768+0 records out<br>
</div>34359738368 bytes (34 GB) copied, 57.7027 s, 595 MB/s<br>
(wow!!)<br>
<br>
During the whole write time both CPU cores were 90-100%, mostly 95-99%!<br>
Glad to see RAID/XFS code is multi-core aware. For reading it was 1<br>
core at 100% and the other around 20%. The write limiting factor<br>
appears to be my piddly Pentium D on my file server. Still, this is<br>
3-4X the speed my old (1TB drives, crappy PCI SATA cards) array was<br>
giving me. The read is quite interesting in that the 100% CPU<br>
indicates it is probably doing parity checks on every read.<br>
<br>
I think a big part of the good speed is my new 8-port SATA card, an<br>
Intel PCI-Express x 8 in a x8 slot. If your SCSI card is just PCI,<br>
then the PCI MB/s speed limit is what's killing you. Even PCI-X may be<br>
limiting. And the Intel card was pretty cheap, under $200.<br>
<br>
BTW, I got stuck with two spare SATA card expander cables (1 card<br>
port to 4 SATA drives) if anyone wants some cheap. I can get in the<br>
Intel cards too, if anyone wants a complete package.<br>
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