Nexus 5596T split core (multiple hops) reasonable for ISCSI traffic

[will]

I'm piecing together a proposal for a new network which is comprised of two mini-datacenters separated by about 50 meters. All the SAN storage is in one location (DC1) and the accessing hosts are in both locations (DC1 & DC2). All SAN traffic is ISCSI over SFP twinax and 10Gbase-T.

the design would look kind of like this:

                 ---------------------------------------DC2---------------4x40Gb--------DC1------------------------------

Unified network host----------2200 FEX --------- 5596T ========== 5596T --------- SAN Appliance

= is a 4x40 Gb link with N55-MQ4 module in Nexus 5596T

- is a 10Gb link over SFP+ or 10Gbase-T copper.

hosts would directly connect to the 5596T switches as well.

Does anyone see any potential pitfalls with this configuration? ISCSI over multiple hops is one concern.

Any potential latency issues? the 4x40GB interconnect between 5596T is another concern.

Anyone doing anything like this and has positive/negative feedback would be much appreciated.

thx in advance,

Will

[Walter Dey · Accepted solution]

Hi Will

Multihop is not a problem.

I would be more concerned with HA, e.g.

- are your servers dual homed ?

- did you take oversubscription of the FEX into consideration

- what happens if you need to do a firmware upgrade of any network component ?

- what are your single point of failures ? 5596 !!

A better solution (but more expensive of course) would be to have 2 5500 per DC

Walter.

[will]

hi walter, thx for reply! In the drawing above, I simplified the design for academic purposes. the plan would be to have two 5596's in each datacenter, with an 80Gb vPC between them. Oversubscription was considered and all servers would be dual-homed.

My real concern was the ISCSI over longer distance/multihop with a fiber connection between the two 5596T's. I cannot easily find any good info on ISCSI over multi-hop Layer2.

thx again!

Will

[Walter Dey · Accepted solution]

Hi Will !

iSCSI is TCP/IP; therefore you could even run it between IP subnets (router) without a problem.

Don't worry about multihop latency ? your disk latency will be much much higher.

You should really be concerned about Vlan's aross 2 DC's and spanning tree.

In your case, you could go for vPC's which would resolve above issues.

Good luck

[will]

thx again Walter!