# Storage &amp; Capacity

Discussion in 'General DBA Questions' started by Eddy!, Jul 22, 2009.

1. ### Eddy!New Member

We are looking at purchasing a SAN therefore i am beginning to gather some stats to help with the storage/capacity planning.

Iam currently using perfmon to retrieve disk reads/sec and diskwrites/sec to discover how many IOPS our database server is doing.

HoweverI have read in text books and on the web that to work out the currentops per disk depending on RAID levels I would need to use the followingformulas:

RAID 1:
operations per disk = (reads + (2 * writes)) / 2
RAID 10:
operations per disk = (reads + (2 * writes)) / number of disks

A sample of data at a certain time from one of our drives that is a RAID 10 of 4 disks is:

disk read/sec = 2939 and disk write/sec = 480

So to find the IOPS placed on each disk at that time would i simply do:

(2939 + (2 * 480) / 4
= 975 IOPS

And then to figure out how many disks i ideally need given they do roughly 180 IOPS would i use the following formula:

(2939 + (2 * 480) /180
= 22 disks

I would appreciate any feedback, comments on this to point me in the right direction.

Thanks in advance
2. ### Luis MartinModerator

What you read on the web, is valid for SAN?
I suggest to read: http://www.sql-server-performance.com/articles/per/system_storage_configuration_p1.aspx