On Thu, 27 Apr 2006, Rob wrote:
Hello,
I have a cluster, master + 8 nodes, connected via
a Netgear Gigabit Ethernet Switch (model JGS516).
The cables are of CAT5 type.
Elsewhere I read that for a gigabit network, one
should use CAT6 type cables, to avoid bad
transmissions. Is that so?
Not really. The symbol rate for gigabit ethernet is actually the same as
100Mb/s ethernet, (125mhz) and should run for similar distances over the
same cable. using "better cable" buys you squat if your bit-error rate is
currently zero...
I already have done basic speed checks, that indicate
a throughput of about 0.5 Gbps. Hence the network
appears to operate on half of its spec. speed.
Question 1:
Should I worry about this reduced speed?
Are your cards in 32 bit 33mhz pci slots?
In general that's about what you can expect without careful selection of
the hardware involved.
Question 2:
How to check the transmission quality?
Do you see errors in any significant rate on any of your interfaces?
Duplex mismatches are rare with gigabit ethernet,
Should I inspect the output of "/sbin/ifconfig eth0"
for errors/dropped/overruns/collisions etc. in the
RX/TX lines?
If your error rates increment rapidly while sending data then yeah you may
have an issue there.
Lan card info:
master: Tigon3 10/100/1000BaseT Ethernet
tg3: eth0: Link is up at 1000 Mbps, full duplex.
tg3: eth0: Flow control is on for TX and on for RX.
nodes: Realtek RTL8169
eth0: Auto-negotiation Enabled.
eth0: 1000Mbps Full-duplex operation.
Thanks for advice and help!
Rob.
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