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May 12th, 2011 02:00

RAID-Excercise Question-Information Storage and Management Pg. 69

Q. A 10K RPM drive is rated to perform 130 IOPS and a 15K RPM drive is rated to perform 180 IOPS for an application.

The read/write ratio is 3:1. Compute the RAID-adjusted IOPS for the 10K and 15K drives for RAID1,RAID5 and RAID 6.

Actually m not able to find out the formula in which the above parameters are to be set??? Help...

16 Posts

May 22nd, 2011 03:00

Hi Ankit,

The formula is related to the I/O penalties on different RAID configurations

RAID 1 (Mirroring):

     for every write you have an additional write penalty.

     10K --> (130*(3/4)) + (130*(1/4)*2) =

     15K --> (180*(3/4)) + (180*(1/4)*2) =

RAID 5 (striping with parity):

     for every write have a penalty 4 writes.

     10K --> (130*(3/4)) + (130*(1/4)*4) =

     15K --> (180*(3/4)) + (180*(1/4)*4) =

1 Message

February 6th, 2012 10:00

In those formulas, say for instance the RAID1 10K example, the formula would work out to an answer of 162.5.  So the RAID adjusted IOPS is a HIGHER number than where it starts off at??  That doesn't seem right...

It seems in this example you're using the formula that is used on Pg. 67 of the ISM book to actually figure application IOPS requirements.  Is that really the formula to use to derive the answer to this question that is strictly about drives?

Any clarification would be great.

Thanks!

Lee

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