06-20-2013
Parkinson's law: need expands to consume excess resources.
Companies like Akamai make a good living ensuring your static web hits are filled from relatively local cache servers.
Good architectural design has to deal with:
- having a soft saturation, so throughput goes up to saturation and then excess load is shedded in a least-lost-value basis, like newest clients lower in priority than older clients (deeper into transaction process).
- avoiding negative saturation behaviors like overloaded Ethernet, which actually slows down due to collisions creating lost time on wire. Positive saturation behavior means the higher the overload, the more efficient the process. Requests can be sorted to they have higher locality of reference. Sometimes, requests for the same file can be mbone multicast as one. Sorting by disk position means shorter seeks.
- flow control mechanisms allow services beyond capacity to be queued for eventual fulfillment, but service cancellation is quickly forearded to the server. The bad behaviors are thing like sending service requests every n seconds until a reply is received, consuming precious bandwidth and cluttering the server with cancelled, redundant, prior requests. Some routers can stifle keep-alive traffic, say from tcp connections of queued services, so they do not drag down net speed.
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NFSD(8) BSD System Manager's Manual NFSD(8)
NAME
nfsd -- remote NFS server
SYNOPSIS
nfsd [-6rut] [-n num_threads]
DESCRIPTION
nfsd runs on a server machine to service NFS requests from client machines. At least one nfsd must be running for a machine to operate as a
server.
Unless otherwise specified, four servers for UDP transport are started.
The following options are available:
-r Register the NFS service with rpcbind(8) without creating any servers. This option can be used along with the -u or -t options to
re-register NFS if the portmap server is restarted.
-n Specifies how many server threads to create. The default is 4. A server should run enough threads to handle the maximum level of
concurrency from its clients.
-6 Listen to IPv6 requests as well as IPv4 requests. If IPv6 support is not available, nfsd will silently continue and just use IPv4.
-t Serve TCP NFS clients.
-u Serve UDP NFS clients.
For example, ``nfsd -t -u -n 6'' serves UDP and TCP transports using six threads.
nfsd listens for service requests at the port indicated in the NFS server specification; see Network File System Protocol Specification, RFC
1094 and NFS: Network File System Version 3 Protocol Specification.
The nfsd utility exits 0 on success, and >0 if an error occurs.
SEE ALSO
nfsstat(1), nfssvc(2), mountd(8), rpcbind(8)
HISTORY
The nfsd utility first appeared in 4.4BSD.
BSD
March 17, 2008 BSD