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Calculate IOPS

Publication Date:  2014-09-17 Views:  376 Downloads:  0
Issue Description
Information needed about IOPS for a specific RAID group .
Alarm Information
Dear TAC,

Please help to answer following customer inquires about our storage performance.
Do you know what approximate amount of IOPS and latency I should be getting for a RAID50 configuration using 18 disks split into 6 disks per raid 5 group?

Handling Process
To calculate the IOPS for this kind of case is very much dependent on the read and write operations. Because the RAID 5 has 4 IO penalties for the write operations , with other words for each write operation the raid controller does 4 IOs , I will further describe some situations in which the IOPS change dramatically.

The stand alone disk has a minimum performance of 175 IOPS , a median of 193 and a maximum of 210 IOPS. According to this 3 values we will next have 3 values for each situation.

Total Raw IOPS = Disk Speed IOPS * Number of disks
Functional IOPS =(((Total Raw IOPS×Write %))/(RAID Penalty))+(Total Raw IOPS×Read %)
Root Cause
There are three different scenarios regarding the customer question depending on the percentage of read/write operations . Since read operation has no penalties the read IO will give a bigger IOPS than the write IO.

These are the values that the customer could meet:

1st  scenario .

All operations are READ. Then the RAID group has a Min performance of 3150 IOPS , Med 3465 , Max 3780 IOPS.

2nd  scenario

50% read operations – 50 % write operations.

Min     1968   IOPS
Med    2166   IOPS
Max    2364   IOPS

3rd scenario

All operations are WRITE.

Min    789
Med   867
Max   945