Merry Christmas to everyone! I am currently studying for the EMCISA certification and I am using "Information Storage and Management: Storing, Managing, and Protecting Digital Information in Classic, Virtualized, and Cloud Environments" as my study guide.

I have a question regarding the chapter 3 question 6 exercise. It reads as follows:

"6. An application has 1,000 heavy users at a peak of 2 IOPS each and 2,000 typical users at a peak of 1 IOPS each. It is estimated that the application also experiences an overhead of 20 percent for other workloads. The read/write ratio for the application is 2:1. Calculate the RAID corrected IOPS for RAID 1/0, RAID 5, and RAID 6."

I understand that the total IOPS is 4800 and I understand that I need to know the write penalty of RAID 1/0 (2), RAID 5 (4), and RAID 6 (6). The formula given by the author to calculate RAID corrected IOPS is this:

% reads (IOPS) + write penalty (% writes X IOPS)

The question specifies that the read/write ratio for the application is 2:1 (but the study guide doesn't appear to cover that information). Did I miss something?

If I put that information into the formula for RAID 5 I get the following:

0.66 (4800) + 4 (0.33 X 4800) = 9504

Is this correct? I am having difficulty with this question because I believe that the read/write ratio corresponds to the % reads and % writes BUT these percentages are not whole numbers (if you divide 100/3 you get 33.3).

What information am I missing? I can't seem to wrap my mind around this.

Is there a different formula I should be using?

Any help is much appreciated!

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