We’re having more and more customers asking for iSCSI switches for their data centers, and the only requirements ever mentioned are “non-blocking/line rate.” The 2960-S (for example) would work for this at Layer 2, but I've heard concern from various resources (outside and within Cisco) about these not being viable for a data center iSCSI application.
The concerns always revolve around buffering capability, and I've been pointed consistently towards a Nexus 5K or Catalyst 2360 solution. Let's focus on the 2360 for now. The datasheet - http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps10920/datasheet_c78-599610.html is almost identical to the 2960-S from a performance perspective, one notable difference being that the 2360 can support 4x10-GE uplinks (2x 10-GE for the 2960-S), the other being mention of “Dynamic Buffer Allocation – all ports are allocated reserved buffer space, and additional buffering is allocated from a shared pool."
The 2960-S 48-port (non-PoE) 10-GE switch lists at $6,995, while the comparable 2360 48-port comes in at $8,695. I recognize the extra two 10-GE ports are worth something (providing close to 1:1 subscription), but I need some serious additional detail regarding the buffering benefit in an iSCSI environment. We've sold 2960-S switches into iSCSI roles in the past, and they've always worked fine - the iSCSI traffic in most data centers never comes close to pushing the capacity of the switch (so the dynamic buffering would never come into play, in my opinion).
Simply put - I need more detail as to why a 2360 or Nexus 5000 would be a "better" iSCSI switch, when most of the traffic between servers and storage within the data center would never cross the 10-GE uplinks anyway. Moving forward, I’d like to be able to have the discussion and explain to the customer what the potential risks/benefits are between these two solutions (2960-S vs. a 2360, for example) in an iSCSI deployment. There have to be more detailed docs around that explain why a particular switch will better fit the bill - if it’s buffering, then HOW much buffering would fit the bill, etc.
This is what I can’t seem to find. Just an hour ago, our team received a customer support issue with the 3750-X switch (again, line-rate/non-blocking) family having issues with dropped frames (worse performance) when enabling jumbo frames.
Thanks in advance!