iSCSI Software Adapter or Broadcom iSCSI adapter?

[stkristobal]

This is a bit of a follow up thread on an earlier post. But I see that my 5 BL490c G6 hosts have listed both a software adapter and Broadcom iSCSI Adapter. Though I have nothing listed under the Broadcom adapters.

Is there a performance difference between these two? In my head, hardware should be better than software, but it seems to default to software.

I found this KB, indicating there may be some fiddling involved to get ESX to use the Broadcom adapters, but is it worth it?

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=102564...

The iSCSI SAN is a StorageWorks P4300 G2.

[logiboy123]

You need to confirm if your adapters are actually full blown HBA's or if they are just GB NIC's with TCP offload support. If they are NIC's with offload capabilities then you are probably going to better off using the software adapter.

Some interesting points in regards to this:

1) It is not supported by VMware to use both software and hardware adapters in a host at the same time. You must use one or the other, not both. This may have changed in vSphere5 but I haven't found anything to confirm this yet.

2) Software adapters use use CPU cycles, however most environments are RAM constrained, not CPU constrained so this is hardly ever a real concern.

Regards,

Paul

[stkristobal]

Paul,

Thanks for clearing that up! They are ordinary mezzanine nics, so I'd imagine we'd have to lash out on proper iscsi accelerators for it to be worth it.

I won't spend any time digging at that then. Thanks again for your help!

-K

[VeyronMick · Accepted solution]

The BCM5709 and equivalents can slightly reduce the amount of work the CPU has to do but don't support Jumbo Frames.

If you're network switches or array don't support Jumbo Frames then using the offload capabilities of these NICs is good.

If Jumbo Frames is supported by both switches and array then using the software iSCSI HBA is preferred.

[stkristobal]

Thanks! I'm much wiser now, and that saved me some hassle reconfiguring

[vlho]

Hi stkristobal,

you look here: http://www.vmadmin.co.uk/vmware/35-esxserver/252-esxihwswiscsijumbo
There is nice article about question: iSCSI Software adapter with Jumbo Frame or Hardware dependant iSCSI Initiator without Jumbo Frame?
Those conclusion is for vSphere version 4.1

Who knows whether is Broadcom BMC series supported with Jumbo Frame in vSphere 5.0?
Any link?

Thanks

[Bulgie]

Anyone know if it is possible to configure the BCM5709 to NOT be seen as an iSCSI adapter in ESXi?  Mine is a 4-port and so I have 4 bogus (unused) Broadcom iSCSI adapters listed in Storage Adapters.  I am using them as regular NICs.

In case it matters, these are embedded in an HP DL360 G7.  I looked for some option ROM prompt at boot but didn't see a chance to configure the NICs to just be NICs...

Thanks!