We are seeing a substantial difference in performance when we perform a read/write to /dev/mapper/... vs. the specific device (/dev/sdXX)
What can we do to further isolate the issue?
We are using CentOS 6.4, with all updates, 2 CPUs, 4 FC ports:
Here's a table comparing the results:
|
# of LUNs |
# of Paths per device |
Native Multipath Device |
IO Pattern |
IOPS |
Latency Micro |
BW KBps |
|
4 |
16 |
No |
100% Read |
605,661.4 |
3,381 |
2,420,736 |
|
4 |
16 |
No |
100% Write |
477,515.1 |
4,288 |
1,908,736 |
|
8 |
16 |
No |
100% Read |
663,339.4 |
6,174 |
2,650,112 |
|
8 |
16 |
No |
100% Write |
536,936.9 |
7,628 |
2,146,304 |
|
4 |
16 |
Yes |
100% Read |
456,108.9 |
1,122 |
1,824,256 |
|
4 |
16 |
Yes |
100% Write |
371,665.8 |
1,377 |
1,486,336 |
|
8 |
16 |
Yes |
100% Read |
519,450.2 |
1,971 |
2,077,696 |
|
8 |
16 |
Yes |
100% Write |
448,840.4 |
2,281 |
1,795,072 |
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