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Rich_T_187288's avatar
Rich_T_187288
Icon for Nimbostratus rankNimbostratus
Apr 01, 2015

Newbie question about LTM load balancing

Hi,

We currently have pools and nodes configured as follows, where there is one primary server and one secondary server.

The resulting load balancing algorithm is only really achieving a failover, where the primary server is always used, unless that has a problem, in which case the secondary server is used instead:

ltm node /Common/primary {
    address PR.IM.IP.186
    description "Server name is primary server"
    ratio 65535
ltm node /Common/secondary {
    address SE.CO.IP.186
    description "Server name is secondary server"

ltm pool /Common/service_Pool {
    load-balancing-mode ratio-node
    members {
        /Common/primary:80 {
            address PR.IM.IP.186
            priority-group 1
        }
        /Common/secondary:80 {
            address SE.CO.IP.186
            priority-group 2
        }
    }
    min-active-members 1
    monitor /Common/http

Please could someone advise me on how to have a number of primary servers and a number of secondary secondary servers.

In F5 config language, I am looking for the below, but don't know what to set the ratio & priority-group numbers to and also if I need to have a different load-balancing-mode and min-active-members settings:

ltm node /Common/primary1 {
    address PR.IM.IP.186
    description "Server name is primary1 server"
    ratio ????
ltm node /Common/primary2 {
    address PR.IM.IP.187
    description "Server name is primary2 server"
    ratio ????
ltm node /Common/primary3 {
    address PR.IM.IP.188
    description "Server name is primary3 server"
    ratio ????

ltm node /Common/secondary1 {
    address SE.CO.IP.186
    description "Server name is secondary1 server"
    ratio ????
ltm node /Common/secondary2 {
    address SE.CO.IP.187
    description "Server name is secondary2 server"
    ratio ????
ltm node /Common/secondary3 {
    address SE.CO.IP.188
    description "Server name is secondary3 server"
    ratio ????

ltm pool /Common/service_Pool {
    load-balancing-mode ratio-node
    members {
        /Common/primary1:80 {
            address PR.IM.IP.186
            priority-group ?
        }
        /Common/primary2:80 {
            address PR.IM.IP.187
            priority-group ?
        }
        /Common/primary3:80 {
            address PR.IM.IP.188
            priority-group ?
        }
        /Common/secondary1:80 {
            address SE.CO.IP.186
            priority-group ?
        }
        /Common/secondary2:80 {
            address SE.CO.IP.187
            priority-group ?
        }
        /Common/secondary3:80 {
            address SE.CO.IP.188
            priority-group ?
        }


    }
    min-active-members 1
    monitor /Common/http

Thanks in advance.

application delivery
design
LTM

2 Replies

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  • Ed_Summers's avatar
    Ed_Summers
    Icon for Nimbostratus rankNimbostratus
    Apr 01, 2015

    You can use the 'priority group' feature to accomplish having a "primary" and "secondary" group of servers. Simply have your "primary" servers in priority group 100 and secondary servers in priority group 50, for example. (Note that the priority groups are used in order of HIGHEST priority.) 'Min active members' determines when the next priority group of servers comes online to accept connections. Once the available members in priority group 100 falls below 'min active members', BigIP brings the next group online for connections. In your example, the servers in priority group 2 will be active first, then priority group 1 active should the 'min active members' in group 2 fall below the level you set. Some additional info is available at:

     

    https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-concepts-11-1-0/ltm_pools.html1216212

     

    The 'ratio' setting is related to the load balancing method, and does not determine when priority groups are activated. It relates to the ratio of new connections each server in a pool will receive. A common example used for 'ratio' LB methods is servers having differing performance characteristics. Ratio can weight connections more heavily to some servers over others to allow more 'powerful' servers to get more connections. You have not indicated such a case in your description so I am not sure that a 'ratio' LB method is right for your environment. The round-robin LB method will work fine with priority groups if your servers have similar characteristics.

     

    Hope this helps...?

     

  • Rich_T_187288's avatar
    Rich_T_187288
    Icon for Nimbostratus rankNimbostratus
    Apr 02, 2015

    Hi Ed,

     

    Thanks very much for this, really helpful and will get me going.

     

    Cheers,

     

    Richard.