How i can define performance thresholds on DiskGroup?

[Andreag_77]

Hi,
someone can says me if is possible get some disks performance indication (IOPs, Queue,etc) for my EVA4000 and DiskGroup with num.30 of 300Gb Fibre Channel Disk (raid 5)?

If i want to define thresholds for evaperf, i need to know limit of my Diskgroup performance, but how i retrive it?

thanks very much
Andrea

[Patrick Terlisten · Accepted solution]

Hello,

you can calculate it with a simple formula. But this will give you only a reference value:

IOPS = (1 / [rotation latency + average seektime]) x 1000

You can calculate the rotation latency like this (for a 15k upm drive):

rotation latency = (1 / [ RPM / 60.000 ms]) / 2

For a 15k upm drive you will get 200 IOPS. For a disk group with 30 drives you will achieve up to 6000 IOPS. So you can set a treshhold of 6000 IOPS for a disk group, and 200 IOPS for a drive.

Best regards,
Patrick

[Andreag_77]

Thanks very much Patrick!

but your formula is adaptable for 10k upm also?

[Uwe Zessin]

Sure. The basic hardware is the same - the platters just don't spin as fast and the seek times might be different.

[Andreag_77]

Sorry, you have defined that IOPS for 15k is about 200 for single disk, but i have disks of 10k RPM and i don't know average seektime..
please, how i can get this info? have you this informations?

thanks again

[Patrick Terlisten]

Hello Andrea,

you can take the average seektimes for the 15k 3,5" SAS drives. Those drives should be comparable to the 15k 3,5" FC drives.

http://h18000.www1.hp.com/products/quickspecs/12244_na/12244_na.html

Best regards,
Patrick