ASM performance check

Database performance is highly dependent on the underlying hardware’s health and the way it was designed and implemented. This post will focus on ASM performance.

For those like me lucky enough to have Enterprise Manager collecting historical statistics, the ASM performance tab can give you a nice, consolidated image of the averaged performance in the last minutes and hours.

Another nice tool to have in the database servers is OSWatcher, a set of scripts that Oracle guys compiled to gather CPU/memory/network/IO information in regular intervals and store it in text files you can look later. You can download it from Oracle Support site.

And if you need the “right here, right now” performance metric of ASM? You can check the gv$asm_disk view in the database itself. The issue is that this view only shows the cumulative values for each disk, not much help alone. To be able to see the last minute numbers, I’ve written a script that gathers these numbers, store in variables, waits 60seconds, gathers new numbers and show you the difference:

ASMperf

Some people asked me what are good values for the average read and write times. I always say that it varies. Depends on the hardware you’ve got. You have to be aware of what are the normal timings of your system to be able to know when it is off the tracks.

DISKGR      READS     WRITES READ_MB/s WRITE_MB/s READ_AVG_SPEED_MSEC WRITE_AVG_SPEED_MSEC AVG_RESP_TIME_MSEC
------ ---------- ---------- --------- ---------- ------------------- -------------------- ------------------
DATA       185017       6203     218.0        1.5               0.018                0.022              0.018

Above is a dummy example of a system pulling 185k reads in one minute (218 MB/s) and still with nice average read and write timings.

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