disk parameters
select a sample disk or put values manually Seagate Savvio® 15K.2 147GB Seagate Cheetah® 15K.7 450GB Seagate Cheetah® NS.2 10K 600GB Seagate Barracuda® ES.2 1TB Seagate Barracuda® LP 2TB
capacity (GB)
rotation speed (RPM)	4200 5400 5900 7200 10000 15000 20000
average seek latency (ms)
array parameters
number of disks
RAID level	0 10 5 6 +
stripe size (KiB)	8 16 32 64 128 256 512 1024 2048 4096
workload parameters
reads (%)
writes (%)
read cache hit ratio (%)
write cache hit ratio (%)
average I/O size (KiB)	1 2 4 8 16 32 64 128 256 512 1024
application block size (KiB)	0.5 1 2 4 8 16 32 64 128 256 512 1024
host parameters
number of FC ports
average I/O service time (ms)
FC port queue depth
lun queue depth

disk results
capacity (GiB)
average random IOPS
access density (IOPS/GiB)
array results
native capacity (GiB)
usable capacity (GiB)
workload results
average random IOPS
average throughput (MiB/s)
host results
maximum host IOPS
maximum lun IOPS

This tool is used for estimating the efficiency and capacity of disks and disk arrays. The results will appear automatically when you type the value of the required parameters.

I appreciate any feedback, suggestions, bug reports.

Move the mouse pointer over the results to see how they are counted.

real disk capacity (GiB)

Disk capacity presented by the manufacturers of these devices is expressed in GB or TB. These units are created by increasing the power of the number 1000. Meanwhile, the computers shows the size of disks in MiB (gibibyte) or TIB (tebibyte). They are formed by increasing the power of the number 1024. For the binary system it's more natural. Read more at Wikipedia

GiB (gibibyte) = 1024 * 1024 * 1024 B
diskGiB = (diskGB * 1 GB) / GiB

average random disk IOPS

Average random Input / Output Operations Per Second. This is a parameter specifying the hard disk performance. This is calculated based on values of the delays generated by the moving drive parts - rotating disk and positioning the head.

rotationLatency = 1 / diskRPM / 60 / 2
diskIOPS = 1 / (rotationLatency + diskSeekLatency)

disk access density

Access Density is the ratio of performance, measured in I/Os per second, to the capacity of the drive, currently measured in gigabytes (Access Density = I/Os per second per gigabyte).

diskAccessDencity = diskIOPS / diskGiB

native array capacity (GiB)

Raw capacity of the array, without RAID protection, spare disks and so on.

arrayNativeCapacity = disks * diskGiB

usable array capacity (GiB)

After formatting the matrix in a RAID level, so much disk space remains for the data.

arrayUsableCapacity = disks / (parityDisks + dataDisks) * dataDisks * diskGiB;

average random array IOPS

writeIO:
     1 if raid0
     2 if raid10
     4 if raid5
     6 if raid6

arrayIOPS = (disks * diskIOPS) / ((1 + ((ioSize * 1 / appBlockSize) - 1) / (stripeSize * 1 / appBlockSize)) * reads / 100 * (1 - readCacheHitRatio / 100) + writeIO * ( 1 + ((ioSize * 1 / appBlockSize) - 1) / (stripeSize * 1 / appBlockSize)) * writes / 100 * (1 - writeCacheHitRatio / 100))

average array throughput

arrayThroughput = arrayIOPS * ioSize

maximum host IOPS

hostIOPS = 1 / averageServiceTime * fcPortQueueDepth * fcPorts

maximum lun IOPS

lunIOPS = 1 / averageServiceTime * lunQueueDepth

Copyright © 2009 Marek Wołynko