As per the following article, MS make recommendations regarding storage for the Exchange 2010 MBX role:
http://technet.microsoft.com/en-us/library/ee832792(v=exchg.141).aspx
This post pertains specifically to the recommendation for the disk timeout value. By default this is set at 60 seconds. For DAS or SAN this should be modified to 20 seconds. I have created a one liner to do this:
Set-ItemProperty -path HKLM:\SYSTEM\CurrentControlSet\services\Disk -name TimeOutValue -value 20
More info on the topic can be found here:
http://blogs.msdn.com/b/san/archive/2011/09/01/the-windows-disk-timeout-value-understanding-why-this-should-be-set-to-a-small-value.aspx
Note that the information is omitted from the Exchange 2013 version of the Technet article:
http://technet.microsoft.com/en-us/library/ee832792.aspx
Don't ask me why. I can't see that it wouldn't still be relevant. If you're looking at this in reference to Exchange 2013, read the blog and make up your own mind. Personally, I would still set it to 20 seconds in the absence of specific advice.
Wow. Is it only five to four? I've got another five minutes of work. Time for a coffee...