Re: 5400RPM|7200RPM Cable bottleneck?

[Lars Eggert]

On 1/18/2003 2:27 PM, Terry Lambert wrote:

Lars Eggert wrote:

I've tried NFS mounting ISI servers at home over PPTP over a cable modem
connection, and it's painfully slow - much slower than the bandwidth of
the cable pipe. NFS isn't well tuned for high-RTT environments (in my
case, 20ms).

The up-channel speed on a cable modem is usually in the
neighborhood of 1.5 times the amount of bandwidth needed
for just the ACKs for the data coming down the down-channel;
that leaves very little bandwidth left over for NFS requests
to the server, particularly if there are a lot of data
transfers taking place from the server to the client (client
reads).  If you are doing any level of data transfers from
the client to the server (client writes), you should expect
your performance to go to hell.

Both uplink and downlink bandwidths are nowhere near saturation - it's the underlying RPC that make NFS inherently slow over WAN links.

Lars
--
Lars Eggert <[EMAIL PROTECTED]> USC Information Sciences Institute

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