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Younes
Asked: 2019-01-24 12:41:01 +0800 CST

keepalived：什么是 `fo` 和 `mh` lvs 调度算法？

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keepalived.conf 中的参数virtual_server.lvs_sched支持两个我找不到解释的选项： fo和md.

有人知道它们的含义吗？

keepalived

1 个回答

  1. Best Answer

    允许的值virtual_server.lvs_sched是 IPVS（IP 虚拟服务器）调度程序的名称。keepalived手册页提到 rr|wrr|lc|wlc|lblc|sh|mh|dh|fo|ovf|lblcr|sed|nq了调度程序的受支持名称，这比原始 IPVS 文档描述的要多得多。

    我不得不看一下内核源代码，以了解那些较新的调度程序是什么：

    • fo是“加权故障转移”——所有其他调度模块都实现了某种形式的负载平衡，而这提供了一个简单的故障转移解决方案。加权故障转移调度算法将网络连接定向到当前可用权重最高的服务器。
      来源：https ://patchwork.ozlabs.org/patch/390597/

    • mh是“磁悬浮哈希”

      /* The mh algorithm is to assign a preference list of all the lookup
 * table positions to each destination and populate the table with
 * the most-preferred position of destinations. Then it is to select
 * destination with the hash key of source IP address through looking
 * up a the lookup table.
 *

      该算法详述于：3.4 一致性哈希

    为了完整起见，ipvasdm 手册页提供了其他调度程序的描述：

              scheduling-method   Algorithm for allocating TCP connections and
          UDP datagrams to real servers.  Scheduling algorithms are imple-
          mented as kernel modules. Ten are shipped with the Linux Virtual
          Server:

          rr - Robin Robin: distributes jobs equally amongst the available
          real servers.

          wrr - Weighted Round Robin: assigns jobs to real servers propor-
          tionally to there real  servers’  weight.  Servers  with  higher
          weights  receive  new  jobs first and get more jobs than servers
          with lower weights. Servers with equal weights get an equal dis-
          tribution of new jobs.

          lc  -  Least-Connection:  assigns more jobs to real servers with
          fewer active jobs.

          wlc - Weighted Least-Connection: assigns more  jobs  to  servers
          with  fewer  jobs  and  relative  to  the  real  servers’ weight
          (Ci/Wi). This is the default.

          lblc - Locality-Based Least-Connection:  assigns  jobs  destined
          for  the same IP address to the same server if the server is not
          overloaded and available; otherwise assign jobs to servers  with
          fewer jobs, and keep it for future assignment.

          lblcr   -   Locality-Based  Least-Connection  with  Replication:
          assigns jobs destined for the same IP address to the  least-con-
          nection  node  in  the server set for the IP address. If all the
          node in the server set are over loaded, it picks up a node  with
          fewer  jobs  in the cluster and adds it in the sever set for the
          target. If the server set has not been modified for  the  speci-
          fied  time, the most loaded node is removed from the server set,
          in order to avoid high degree of replication.

          dh - Destination Hashing: assigns jobs to servers through  look-
          ing  up a statically assigned hash table by their destination IP
          addresses.

          sh - Source Hashing: assigns jobs to servers through looking  up
          a statically assigned hash table by their source IP addresses.

          sed  -  Shortest  Expected Delay: assigns an incoming job to the
          server with the shortest expected delay. The expected delay that
          the  job  will  experience  is (Ci + 1) / Ui if  sent to the ith
          server, in which Ci is the number of jobs on the the ith  server
          and Ui is the fixed service rate (weight) of the ith server.

          nq  -  Never Queue: assigns an incoming job to an idle server if
          there is, instead of waiting for a fast one; if all the  servers
          are busy, it adopts the Shortest Expected Delay policy to assign
          the job.
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