Software vs iSCSI HBA (real world performance)

Question

I am setting up an AX150i and wanted to get input from those with real world experience.

Servers will be Dell 1950 with RH Linux.
Is there much real world performance gain to be had using iSCSI HBA (Qlogic) vs software and the existing onboard NICs?

(Enough that it is worth spending another grand per server)

Thanks!
Dana

ecorona1 · Answer

I dare to say no, but it depends on the server and the load that is managing, if you use the software initiator all of your traffic is going thru the same channel and you might have a issue at some point since the OS is managing everything or if you use a dedicated NIC for iscsi there is still some CPU overhead.

this PDFs describes better the diferences between software initiator vs iSCSI HBA initiator.
http://www.sanstor.info/5iSCSI%20software%20initiators%20vs.pdf

fragment from the PDF file:

''There is also a major difference in the CPU overhead between each approach. The
software-only initiator may consume up to 500MHz of CPU for 1 Gigabit Ethernet
line rate. In contrast, with a hardware-assisted iSCSI initiator HBA, the TCP/IP
and iSCSI processing is offloaded to the HBA, resulting in less than 10% CPU
overhead for a 1GHz CPU, which is comparable to that of a Fibre Channel HBA.''

hope it helps.

rhythmrider · Answer

OK, so in other words, if you have the CPU power available, there really isn't much or any performance gain to be had using HBAs.

If, on the other hand, you are CPU bound, then it can be helpful to have the HBA cards.

500MHz out of a pair of dual core 3000Mhz CPUs doesn't sound like much of a performance drain.

Thanks!

CLARiiON

Software vs iSCSI HBA (real world performance)

Was this post helpful?