SAN block size for SQL Server on 4KB NTFS
Quoting from Brent Ozar's article SQL Server Virtualization Q&amp;A:


  Question: “Regarding Virtualization and SAN… is there a recommendation
  for setting block size on SQL Server 2008?”
  
  There’s a few related settings here including NTFS allocation unit
  size, RAID stripe size, and partition offset.  Check with your SAN
  vendor’s documentation to see what’s right for you.  In most cases for
  OLTP databases, you’re in decent shape with 64K NTFS allocation unit
  size and RAID stripe size, and a 1mb partition offset.


So yes, by default you'll be safe with a 64k block size, but see also your storage documentation, maybe they specify some other preferable unit for a database server.

Some more great information from the same blog: SAN Storage Best Practices for SQL Server.