July 13, 2009 at 10:08 am
In the above it says (Avg. Disk Reads/sec) + (Avg. Disk Writes/sec)
I thought these two were how long in seconds is the disk taken.
I see AVG DISK SEC / READ which is how long in seconds disk take..
but not the AVG DISK READ/SEC counter
I have DISK READ SEC but not AVG DISK READ SEC
Physical counters on Permon.
Which one?
July 13, 2009 at 12:39 pm
Avg. Disk Sec/Read and Avg. Disk Sec/Write are the values you're looking for.
However, to see how your disk is performing, it's usually more useful to look at % Disk Time and Avg. Disk Queue Length. The first one is pretty obvious, it shows how busy you're I/O. The second shows how many processes are having to wait to access the disk, reads or writes.
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July 13, 2009 at 9:03 pm
Thanks but i want the IOPS as we only got 420 IOPS and i want to be sure we not reaching these limits.
Cheers
July 14, 2009 at 9:42 am
July 14, 2009 at 12:08 pm
i will look at that counter too.
Is doing the following with the two counters Physical Disk Reads / Sec and Physical Disk Writes/Sec
Then i have all disks information and performing these calucations
Raid 0 -- I/Os per disk = (reads + writes) / number of disks
Raid 1 -- I/Os per disk = [reads + (2 * writes)] / 2
Raid 5 -- I/Os per disk = [reads + (4 * writes)] / number of disks
Raid 10 -- I/Os per disk = [reads + (2 * writes)] / number of disks
(You can use the above RAID calculations to determine the I/Os per disk. 120 reads + (4 * 150 writes) / 4 physical disks = 180 I/Os per disk. This is over the general rule of 125 I/Os per disk capacity. This system has a disk bottleneck.
Not good from my results if above is valid
disk read reads writedisks raid using above calc san iop maximum
194.28498.12Temp DB 21 595.26 160
308425.07Temp DB 21 579.07 160
294.51384.86Temp DB 21 532.12 160
552.12249.49Temp DB 21 525.55 160
DISK TRANSFER / SEC
118.384166191947
3.86856420768792
269.378040336257
(This is 269 IOPS Sec ?)
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