In article , chris-c wrote: :I need some quick advice on upgrading our lan as I am a bit unsure on :a couple of things. We are intending to buy netgear 4 24 10/100 :switches and 2 24 gbit port switches to replace our old ones.
If you intend these to be high utilization devices, then it would be a good idea to buy 1 first and stress test it in your environment. Different Netgear switch models have different quality levels. The further you get from Netgear's traditional consumer-level device, the more caution is advised.
:1) Someone was suggesting not to use the stack ports but just connect :the gbit ports from the 4 10/100 switches to the gbit switches. I am a :bit wary of this and I think this could cause bottleneck - I am :correct? If 10 machines were trying to talk thorugh the gbit port to :the other switches then wouldnt that saturate the link? - whereas if :you used the stackable ports to interconnect the switches this would :not happen?
Switches that are directly stacked will use the local stacking bus to exchange data. The speed of that will depend upon the speed of the stacking bus and upon how it is used [some stacks are sychronous, alloting time for each stacked device in turn, even if they have nothing to say!].
If you have two switches without uplink ports that could stack together but you connect them by way of a different switch, then the latency will be the latency of serializing the data out of switch 1, receiving it and switching it in the core switch, serializing it out of the core switch, and receiving it in the destination switch; the maximum throughput for this operation will be the minimum of speed of the links involved. In the case of the 24-port 10/100 switches, that's going to be a maximum throughput rate of 100 Mbit/s, with latency of two switches serializing for transmission and two switches receiving transmission and one switch switching between ports; add a tinsy bit for the actual wire speed between the devices.
If you stack the two switches together instead, then the latency would be the latency of serializing to the parallel shared bus, and of receiving at the other end of the parallel shared bus, plus an itsy bitsy teeny weeny time for transmission over the 1 metre bus cable. Throughput would be whatever the rate the bus ran at, taking into account parallel transmission rather than serial (e.g., 100 MHz of parallel 8-bit data is equivilent to 800 MHz of bit-at-a-time serial data.)
Stacking busses are usually noticably faster than the fastest port. For example, on the 24 port 10/1000 switch, the stacking bus might run at 1 Gbit/s.
:2) If you do 'stack the switches' then isnt there a redundancy problem :in that in effect the stack ports are daisy chained so if the middle :switch broke this would affect communication between switch 1 and :switch 4? So for redundancy if you elimetaed the stack method but :connecting each switch to the gbit backplane switch, if one of the :10/100 switches died - it would not affect any of the others?
It depends on how the manufacturer impliments stacking. Nortel and Cisco use ring topologies (last device is connected to the first) so there is always a way to get to a device if something in the middle breaks. The better switches automatically manage around failures. For example, Cisco's new "StackWise Technology" is fully able to have a new switch step in quickly as the new master if the master switch fails.
In the star topology you haven't eliminated single points of failure: you've just made the gigabit switch your single point of failure. Considering that gigabit is newer technology that hasn't had as much time to smoke out the bugs, you could be -reducing- your reliability by going star topology instead of stacking well-developed 10/100 switches.