Justin Piszcz schrieb:
On Tue, 25 Sep 2007, Bryan J. Smith wrote:
Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx> wrote:
Just out of curisosity have you tried SW RAID5 on this array?
Also what do you get if you use RAID0 (hw or sw)?
According to him, if I read it correclty, it is an external FC RAID-5
chassis. I.e., all of the logic is in the chassis. So your question
is N/A.
Although I'm more than ready to be proven incorrect.
Furthermore, what benchmark do you use? If dd on the volume itself,
software RAID wins, hands down. Doesn't matter what size you give
it, it literally copies (and doesn't recalculate) the parity. It's
the rawest form of non-blocking I/O, and uses virtually no system
interconnect to the CPU (just pushes disk-mem-disk).
bonnie++, iozone, etc..
all show ~430-460 MiB/s write and ~550 MiB/s read
I'm happy :) I was able to boost the read performance by setting
blockdev --setra 16384 /dev/sdc
I knew this parameter is neccessary for 3ware controllers, but I
haven't noticed any difference with areca controllers or ext. raids yet.
The write performance may not be ideal, but these read numbers makes much
more sense now because the FC controller is the limiting factor.
Sequential Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
----- ----- --- ------ ------ --------- ----------- -------- -------- -----
20000 4096 1 391.20 50.24% 0.019 43.01 0.00000 0.00000 779
20000 4096 2 387.79 92.22% 0.040 278.71 0.00000 0.00000 420
Random Reads
File Blk Num Avg Maximum Lat% Lat% CPU
Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
----- ----- --- ------ ------ --------- ----------- -------- -------- -----
20000 4096 1 2.87 0.698% 2.720 27.47 0.00000 0.00000 411
20000 4096 2 4.37 2.013% 3.473 47.35 0.00000 0.00000 217
Sequential Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
----- ----- --- ------ ------ --------- ----------- -------- -------- -----
20000 4096 1 189.23 42.73% 0.029 5670.66 0.00014 0.00000 443
20000 4096 2 173.92 84.93% 0.064 4590.56 0.00029 0.00000 205
Random Writes
File Blk Num Avg Maximum Lat% Lat% CPU
Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff
----- ----- --- ------ ------ --------- ----------- -------- -------- -----
20000 4096 1 1.85 0.662% 0.011 0.05 0.00000 0.00000 279
20000 4096 2 1.68 0.772% 0.012 0.05 0.00000 0.00000 217
Ralf