There are two SCSI driver standards that are available for most SCSI HBA’s. The older standard (SCSIport) has been replaced by a newer technology (STORport). STORport allows faster I/O, duplexing and other advantages. You should use the STORport drivers for all HBA’s when available. This is especially revelant for FC cards. The details are: [more]

Classic SCSI (SCSIPort):

  • commands were queued on an adapter/LUN basis
  • Maximum number of I/O's per adapter is 256, with 16 LUN's per adapater
  • Queue limit on LUN level, with a maximum of 20 outstanding I/O's
  • If one LUN reaches it's limits all other LUN's will be blocked as well
  • Will remain for direct attached storage


  • No limitation on adapter queues
  • Each LUN has a queue limit of 256 outstanding I/O's
  • Designed for Fibre Channel attached storage
  • Exchange and SQL will probably not be using Storport directly
  • Except for SQL RAW disk functionality which will bypass volume management (for higher performance)

More details: