Performance of 2GB CHIP Pairs on XP512

[Duncan Edmonstone]

Hi,

Recently I've been involved in a SAN migration which happened to involve reconfiguring a bunch of HP-UX volume groups on a XP512. Now originally I thought the XP had the older 1GB CHIP Pairs that most XP512s shipped with, and would therefore need me to balance the LUNs not only across CL1 and CL2, but also balance the number of odd and even LUNs on a adjacent ports on a CHIP (ports A&B, C&D etc.) due to the performance limitations of the i960 ASICs which drive the ports. (see my attached diagram).

However when we determined the system had 2Gb CHIP pairs I wasn't so sure - a chat with an HP engineer indicated that I no longer needed to worry about the i960s on 2Gb CHIPs, and should just balance LUNS across clusters in the usual way. We did this and were surprised to find that our performance was very poor.

So I decided to re-apply the odd/even LUN balancing and this appeared to sort out the problem, which leads me to my question...

Apart from the front-end speed of the fibre ports being 2 rather than 1Gb, are there any other architectural/speed differences between the 1Gb and 2Gb CHIP pairs on a XP512? I presume there must be, as the 1Gb CHIPs couldn't push more that 100MB/s across 2 adjacent ports, never mind 200MB/s required for 2Gb fibre channel. Are the ASICs also faster, but still not fast enough to drive both ports at wire-speed?

Good points for detailed answers, particularly any pointers to reference material.

Cheers

Duncan

[Sanjay Kumar Suri]

Check if this thread helps:

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=47549

sks

[Duncan Edmonstone]

ping... still looking for a definitive response on this...

cheers

duncan

[Duncan Edmonstone]

Never had an answer to this, but still interested... anyone?

Cheers

Duncan

[Vincent Fleming]

Duncan,

As I recall (I've been unable to find documentation to confirm this), the 2Gb CHIP pairs are virtually identical to the 1Gb, other than the FC controller ASIC being 2Gb rather than 1Gb. I forget if the processors are a higher clock rate... I think so - but it's still an i960.

The real changes (ie: different processors) came with the later model XPs.

Cheers,

Vince