Questions on Sequential Disk Spindle I/O for Exchange 2010 Calc tool

When I encountered issues in using Exchange 2010 Calc tool on value setting in Sequential Disk Spindle I/O and found no similar questions raised in the community, I decided to post it out for dicussion.

We always had the separation between DB and Log siznig for Exchange 2010, especially when customers requried. The DB performance sizing we usually rely on random disk spindle I/O, such as ROT defined. But for log disk configuration, it is hard to utilize sequential I/O to estimate size for disks(Because it is not high). Shall we get other metric to determine the disks required for log?(i.e. log size)

We get IOPS in default 300 in Microsoft tool though I have no idea where the value is from and why it is set.