 ## Monday, July 2, 2012

### Formula to calculate Disk throughput, IOPS, MBps and vice versa

couldnt resist borrowing from Dean's Blog

IOPS = Throughput/IO               (all value in kb)
or
IOPS=[MB/KB]*1024 or
IOPS = (MBps Throughput / KB per IO) * 1024 [since 1mb=1024kb]
So here is the calculation I was using:
So using the above, if I wanted to configure an IOPS limit to satisfy a 10 MBps throughput using a 8KB IO request size I would require to set the SIOC IOPS limit to 1280.
First let us convert 10MBps to kbps
10*1024=10240
IOPS = (10240/8)

= 1280
It is possible to use the calculation in reverse to determine the MBps required to achieve the  IOPS claim using the following:
MBps = (IOPS * KB per IO) /1024
In the above example where the requirement is to achieve 1280 IOPS, we would need a throughput of 10MBps to satisfy that claim.
MBps = (1280 * 8) /1024 = 10

http://www.valcolabs.com/2012/05/12/objective-1-1-implement-and-manage-complex-storage-solutions/
• Typically when your workloads are read intensive it is best to use RAID 5 or RAID 6. When the workload is write intensive you want to use RAID 1 or RAID 1+0. Hopefully the application owner can give you the read/write percentages so that you can determine which RAID level is best.
• Here’s an example:
• Formula: (total required IOPs * read%) + (total required IOPs * write% * RAID penalty) = total IOPs required
• 400 IOPs required
• 65% write
• RAID1 = (400 * 0.35) + (400 * 0.65 * 2) = 660 IOPs
• 15K disks required = 4
• 10K disks required = 5
• 7.2 disks required =  9
• RAID5 = (400 * 0.35) + (400 * 0.65 * 4) =  1180 IOPs
• 15K disks required = 7
• 10K disks required = 9
• 7.2 disks required =  16
• RAID6 = (400 * 0.35) + (400 * 0.65 * 6) = 1700 IOPs
• 15K disks required = 10
• 10K disks required = 14
7.2 disks required =  23

 RPM(rotations per minute) speed IOPS SSD 6000 15k 175 10k 125 7200 75 5400 50

 RAID Write Penalty 0 1 1 2 5 4 6 6 DP 2 10 2

(TOTAL IOps × % READ)+ [(TOTAL IOps × % WRITE) ×RAID Penalty]=Total IOPS Required
or