SLOW RESPONSE FROM ASMCMD AND V$ASM% QUERIES
Last updated on JUNE 24, 2009
Applies to:Oracle Server - Enterprise Edition - Version: 10.2.0.3 to 10.2.0.3
Why ASMCMD commands or selects on V$ASM_DISKGROUP or V$ASM_DISK views, are much slower on HP Itanium versus HP-UX PA RISC?
Queries against V$ASM_DISKGROUP, takes 00:00:06.61 seconds
Queries against V$ASM_DISK, takes 00:00:06.23 seconds.
(HP-UX PA RISC):
Queries against V$ASM_DISKGROUP, takes 00:00:00.01 seconds
Queries against V$ASM_DISK, takes 00:00:00.01 seconds.
Regarding the storage used by these servers, both servers are attached to the same storage system. Therefore, all the characteristics/features are the same.
v$asm_alias, in this case is 668.
ASM_DISKSTRING is set equally for both platforms, and is already restricting the discovery path to avoid any further delays when querying the views.
Provided the solution to edit $ORACLE_HOME/bin/asmcmdcore script, and change all references from v$asm_disk or v$asm_diskgroup, to v$asm_disk_stat or v$asm_diskgroup_stat, to speed up these queries. However, this does not explain why the same 10203 code installed on one flavor of HP, will run slower than another flavor of HP.
Issue cannot be reproduced if using local disks (i.e., If one is to dismount the diskgroups from external storage and then create a new logical volume in an internal disk and create a diskgroup with this new
Sar on an OS test of the devices on both platforms, show there is no issue reported at the OS layer. One can do a test by executing the command 'dd if=<device name to test> of=/dev/null bs=48' in each environment. Results from sar were:
Test blks/s avserv(ms)
~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ ~~~~~~~~~~
PA-RISC 162458 0.56
Itanium-external storage 204392 0.45
Itanium-local storage 252017 1.13
Note: blks/s meaning input/output processed blocks per second, and avserv
meaning average time to serve an input/output request. Observe the
Itanium server, in both tests, processes more blocks than PA-RISC, and
Itanium with external storage has the minimum average time to serve a
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