On 02/11/2012 20:10, Jeff Wheeler wrote: > The biggest difference between the TOR-style switches and chassis > offerings, aside from the obvious, is buffers. All the TOR-type 10G > switches have really small buffers and that can be a performance issue > for iSCSI when utilization is high
not particularly when utilisation is high, but in situations where congestion occurs, e.g. when you either have a high write load from multiple clients to a single server, or if you're down-shifting from a 10G server to 1G clients or something. > The vendors will all tell you about lossless ethernet, flow control, > etc. and that crap sounds great on paper. Try making it actually work. flow control on a switch port can lead to hol blocking, which is bad bad news - guaranteed to trash multi-access network performance. Some vendors actually push this as a feature. I don't completely understand why, but maybe it has something to do with customers mistakenly believing that it will make their lives better. People believe in all sorts of odd superstitions though: black cats, spilling salt, having full features on ethernet LAGs, vendor marketing blurb, fear of the number 13, etc. All very odd stuff. Nick
