I am trying to understand the optimal number of disks required in a RAID configuration for an application which has been monitored, at peak time, to have the following IOPS.

The disk subsystem is split in to data on RAID 10, tempdb on RAID 1 and logs on RAID1 or RAID10.

I am using the standard calculation to calculate number of disks required

```
Reads fraction + (Write Penalty * Write Fraction)
```

Number of disks required = ----------------------------------------------------- Single Drive IOPS

It works out as follows with a drive IOPS of 120 :

Data disk

RAID 10

IOPS 240 98% writes 2% reads

Minimal disks required assuming 240 IOPS = 4 Ideal disks required assuming 500 IOPS = 8

TempDB

RAID 1 or RAID 10

IOPS 1.4 49% writes 51% reads Minimal disks assuming 1.4 IOPS = 2 Ideal disks required assuming 3 IOPS = 4

Log Files

RAID 1

IOPS 600 100% writes 0% reads

Minimal disks assuming 600 IOPS = 10 Ideal assuming 1200 IOPS = 20

My question is does this seem correct as per the calculations and how do people implement this kind of setup in the real world. The disk requirement for logs seems huge and overall the ideal implementation would required 32 disks. Would someone realistically buy a server with 32 disks or would some kind of SAN setup be used?

Thanks in advance for any help you can give and sorry for the n00b questions. Any corrections in my assumptions are very much appreciated.