Over the past week or two I just had a gut feeling that one of our databases i/o subsystem was performing slower than it should have been. This is Oracle 11gR2 on Linux 64 bit using ASM with San storage (8 HBA’s). The DASD is RAID 5 sliced into 1.1 tb Lun’s. There are 15 of these Lun’s presented to ASM as Volume’s (asm lib was used).
When I found a window of lower utilization on the server we ran some “Read” tests against the disks. We were getting 2.5 gbs/second and peaked at 2.9 gbs/second. That told me that my gut feeling was not coming from the i/o sub-system.
Some digging reveled the following:
/dev/oracleasm/disks> ls -ltrfa
brw-rw---- 1 oracle dba 253, 28 Sep 26 10:04 VOL9
brw-rw---- 1 oracle dba 253, 30 Sep 26 10:04 VOL8
brw-rw---- 1 oracle dba 253, 32 Sep 26 10:04 VOL7
brw-rw---- 1 oracle dba 253, 24 Sep 26 10:04 VOL6
brw-rw---- 1 oracle dba 8, 29 Sep 26 10:04 VOL5
brw-rw---- 1 oracle dba 8, 31 Sep 26 10:04 VOL4
brw-rw---- 1 oracle dba 8, 33 Sep 26 10:04 VOL3
brw-rw---- 1 oracle dba 8, 19 Sep 26 10:04 VOL2
brw-rw---- 1 oracle dba 253, 22 Sep 26 10:04 VOL14
brw-rw---- 1 oracle dba 253, 23 Sep 26 10:04 VOL13
brw-rw---- 1 oracle dba 253, 25 Sep 26 10:04 VOL12
brw-rw---- 1 oracle dba 253, 26 Sep 26 10:04 VOL11
brw-rw---- 1 oracle dba 253, 27 Sep 26 10:04 VOL10
brw-rw---- 1 oracle dba 8, 20 Sep 26 10:04 VOL1
Take note of the column with the numbers 253 and 8 in it. This is the Agent (Major) number. A 253 is a multi-path’ing device. However, an 8 is a single-path device. We changed these all to 253’s and now the world is a little better place.
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