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
        • 35% read
        • 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
IOPS Required= IOPS*(Read%)+IOPS*write%*Raid Penalty
http://www.yellow-bricks.com/2009/12/23/iops/
http://deangrant.wordpress.com/2012/02/11/a-calculation-for-mbps-to-iops-and-vice-versa/