Justin Piszcz wrote:
Question,
I currently have a 965 chipset-based motherboard, use 4 port onboard
and several PCI-e x1 controller cards for a raid 5 of 10 raptor
drives. I get pretty decent speeds:
user@host$ time dd if=/dev/zero of=100gb bs=1M count=102400
102400+0 records in
102400+0 records out
107374182400 bytes (107 GB) copied, 247.134 seconds, 434 MB/s
real 4m7.164s
user 0m0.223s
sys 3m3.505s
user@host$ time dd if=100gb of=/dev/null bs=1M count=102400
102400+0 records in
102400+0 records out
107374182400 bytes (107 GB) copied, 172.588 seconds, 622 MB/s
real 2m52.631s
user 0m0.212s
sys 1m50.905s
user@host$
Also, when I run simultaenous dd's from all of the drives, I see
850-860MB/s, I am curious if there is some kind of limitation with
software raid as to why I am not getting better than 500MB/s for
sequential write speed? With 7 disks, I got about the same speed,
adding 3 more for a total of 10 did not seem to help in regards to
write. However, read improved to 622MBs/ from about 420-430MB/s.
However, if I want to upgrade to more than 12 disks, I am out of PCI-e
slots, so I was wondering, does anyone on this list run a 16 port
Areca or 3ware card and use it for JBOD? What kind of performance do
you see when using mdadm with such a card? Or if anyone uses mdadm
with less than a 16 port card, I'd like to hear what kind of
experiences you have seen with that type of configuration.
RAID5 is not the fastest at write, there are patches being tested to
improve that.
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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