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mysql+ha. 实现高可用性 http://code.google.com/p/mysql-master-master/

fping README
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Current maintainer and cool feature adder:

ZeroHype Technologies Inc. ([e-mail]) http://www.zerohype.com


fping website:  http://www.fping.com


Original author:  Roland Schemers ([e-mail])
Previous maintainer:  RL "Bob" Morgan ([e-mail])


Suggestions and patches:

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Original README from 1992! 5 years ago? Time flies...

        fping - A tool to quickly ping N number of hosts to determine
        their reachability.

             Roland J. Schemers III - Stanford University
                   [e-mail]

      fping is a ping(1) like program which uses the Internet Control
      Message Protocol (ICMP) echo request to determine if a host is
      up. fping is different from ping in that you can specify any
      number of hosts on the command line, or specify a file containing
      the lists of hosts to ping. Instead of trying one host until it
      timeouts or replies, fping will send out a ping packet and move
      on to the next host in a round-robin fashion. If a host replies,
      it is noted and removed from the list of hosts to check. If a host
      does not respond within a certain time limit and/or retry limit it 
      will be considered unreachable. 

Site
      Stanford University has a large TCP/IP network with over 16,000 
      assigned IP addresses and over 100 IP subnets.

Problem and Issues

      With a large a number of IP addresses in use, its becomes more and
      more time consuming to check on which IP addresses are actively
      in use, and which critical machines (routers, bridges, servers, etc)
      are reachable. One example is we have a program which goes through
      all of our routers arp caches looking for IP addresses that are in 
      use. After finding a list of IP addresses that aren't in any arp
      caches fping can then be used to see if these IP addresses really
      aren't being used, or are just behind the routers. Checking 2500
      hosts (99% of which are unreachable) via ping can take hours.
       
      fping was written to solve the problem of pinging N number of hosts
      in an efficient manner. By sending out pings in a round-robin fashion
      and checking on responses as they come in at random, a large number of 
      hosts can be checked at once.

      Unlike ping, fping is meant to be used in scripts and its
      output is easy to parse.