EqualLogic User Conference - What Makes a Good iSCSI Switch?

I hear this often when people are first getting into iSCSI storage, “What switch should I get?” Here’s what I jotted down from Dell EqualLogic engineers today at the EqualLogic User Conference

iSCSI Best Practices session

NOTES

port buffering ... want inbound and outbound

shared vs dedicated buffer architecture … dedicated obviously better but more $

make sure switches do flow control in BOTH directions in/out

minimize spanning  tree

use rapid spanning tree mode on interswitch links

Trunking - also called ISL, LAG, PaGP, LACP

Best Trunking is 1:1 network capacity
Acceptable trunking is 70-80% of network capacity
So if you have 2 arrays w/ 3x1Gb links, you should have 6Gb between switches (1:1)..or at min 6Gbx.7 (70%)=4.2Gb=5Gb between switches

Trunking < Stacking < Chassis Switch

What makes a good switch???

Buffers = 256K per port (guaranteed) [128-256K ok in 3 or less array setups]

flow control ... at min need receive … both directions best

Check for oversubscription in backplane

for non-stacking switches .. best if they have at least 2 10Gb "uplink" ports

continued on part 2