On Mon, Aug 24, 2009 at 4:59 PM, Nick Hilliard <n...@foobar.org> wrote:
> On 24/08/2009 19:03, Holmes,David A wrote: > >> Additionally, and perhaps most significantly for deterministic network >> design, the copper cards share input hardware buffers for every 8 ports. >> Running one port of the 8 at wire speed will cause input drops on the >> other 7 ports. Also, the cards connect to the older 32 Gbps shared bus. >> > > IMO, a more serious problem with the 6148tx and 6548tx cards is the > internal architecture, which is effectively six internal managed gigabit > ethernet hubs (i.e. shared bus) with a 1M buffer per hub, and each hub > connected with a single 1G uplink to a 32 gig backplane. Ref: > > >> http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801751d7.shtml#ASIC >> > > In Cisco's own words: "These line cards are oversubscription cards that are > designed to extend gigabit to the desktop and might not be ideal for server > farm connectivity". In other words, these cards are fine in their place, > but they are not designed or suitable for data centre usage. > > I don't want to sound like I'm damning this card beyond redemption - it has > a useful place in this world - but at the expense of reliability, > manageability and configuration control, you will get useful features > (including broadcast/unicast flood control) and in many situations very > significantly better performance from a recent SRW 48-port linksys gig > switch than from one of these cards. > > Nick > > We experienced the joy of using the X6148 cards with a SAN/ESX cluster. Lots of performance issues! A fairly inexpensive solution was to switch to the X6148A card instead, which does not suffer the the 8:1 oversubscription. It also supports MTU's larger than 1500, which was another shortcoming of the older card. Mike -- Mike Bartz m...@bartzfamily.net
