Storageworks 4/256 San director maximum number of ports

[jeffturl_1]

I am looking to replace a Storageworks 4/64 full for a Storageworks 4/256 with a number of 4Gb and 8Gb blades.  looking at the following quickspecs:

http://h18000.www1.hp.com/products/quickspecs/12344_na/12344_na.pdf

on page 4 it reads:

Full performance at 4 Gb/s across 128 ports using 16-port 4 Gb/s blades, providing excellent performance
Full performance at 2 Gb/s across 256 ports using 32-port 4 Gb/s blades, providing leading performance and port density
3 to 1 maximum oversubscription ratio with 48-port 4 Gb/s blades for outstanding fan-out scalability

Can someone confirm exactly what this means, if using 4Gb blades can i only have 128ports  as it says 384ports earlier on in the document.  and if i use 48port blades what is meant by the 3 to 1 oversubscription?

Thanks

[Johan Guldmyr]

Hey, http://www.brocade.com/data-center-best-practices/competitive-information/oversubscription.page

this link has details about the oversubscription with a 4/256 (Brocade 48000).

"The Brocade 48000 and Mi10000 directors have 64 Gbit/sec". 

"The 48-port 4 Gbit/sec blade is (at worst) 24:8 over-subscribed when crossing the backplane, and 1:1 subscribed when switching in a 24-port local group."

So if you have over 64/4=16 x 4Gbps ports in a blade, you cannot have all ports operating at 4Gbps if all traffic is non-local.

With careful planning and placement of devices in the blades you can achieve "locality" between most high-traffic ports, this will enable you to get most out of the director.

http://www.brocade.com/downloads/documents/white_papers/48000Architecture_WP_02.pdf

may be of interest to you too.