Tag Archives: performance

Storage FC HBA Transfer Size Tuning

HP just published an advisory describing how to tune some parameters for Emulex, Qlogic and Brocade Fibre Channel HBAs: c02518189. It sounds like these are new, but these changes have been around for at least 6 months in all three vendors’ HBAs.


“Emulex driver version 2.42.002 or later, along with OneCommand Manager version or later,”

Use HBAnywhere to change these.

Examples to tune the server or port level transfer size:

  • 128 kbytes, set the LimTransferSize = 2 and ExtTransferSize = 0 (default)
  • 512 kbytes, set the LimTransferSize = 0 (default) and ExtTransferSize = 0 (default)
  • 1 Mbytes, set the LimTransferSize = 0 (default) and ExtTransferSize = 1


This is part of the Qlogic SANSurfer utility.

  • c:\>qlfc -tsize /fc
  • c:\>qlfc -tsize /fc /set 128
  • c:\>qlfc -tsize /fc /set default


  • bcu drvconf –key bfa_max_xfer_len –val 64
  • bcu drvconf –key bfa_max_xfer_len –val 128