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thornade_91981's avatar
thornade_91981
Icon for Nimbostratus rankNimbostratus
Mar 24, 2009

Active/Active redundant pair and persistence mirroring

Hi,

 

I have configure :

 

- an active/active pair of bigip 3600 LTM

 

- a virtual server active on unit 1 with a default pool p1 and an universal profile u1

 

- a pool p1 composed of 2 web servers

 

- an universal persistence profile u1

 

The "Mirror Persistence" is checked on the u1 profile and an irule is defined.

 

Here is the content of the irule :

 

when HTTP_RESPONSE {

 

set SessionId [HTTP::cookie TestCookie]

 

log local0. "Persist ADD SessionID=$SessionId"

 

if { $SessionId != "" }{ persist add uie $SessionId 1800 }

 

}

 

when HTTP_REQUEST {

 

set SessionId [HTTP::cookie TestCookie]

 

log local0. "Persist IS SessionID=$SessionId"

 

if { $SessionId != "" } { persist uie $SessionId 1800 }

 

}

 

The persistence seems to work correctly when unit 1 is in active state and I could list the persistence table with the following command :

 

b persist all show all.

 

I try the same command on the 2nd unit, but the table is empty. So I have the idea that the persistence table is not mirrored on the second unit, but maybe I'm wrong ?

 

Is there a way to debug mirror persistence on both unit ?

 

Thanks by advanced.
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  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Mar 24, 2009
    I'm not sure if persistence mirroring works for active active. If you configure active-standby, does it work? If you change to source address persistence as a test, do you see the records being mirrored? Which LTM version are you running?

     

     

    I'd suggest not running active-active as it can lead to loss of redundancy if the two units reach 50% capacity. Also in most scenarios the benefit of mirroring persistence for relatively short-lived sessions in HTTP doesn't justify the overhead of copying and maintaining the records on both units.

     

     

    Aaron
  • thornade_91981's avatar
    thornade_91981
    Icon for Nimbostratus rankNimbostratus
    Mar 24, 2009
    Hi, I will test with source address persistence.

     

     

    Concerning, the benefit of mirroring persistence, it makes sense when web servers handle user sessions. In this case, it's important to keep cookie persistence to avoid users login again.

     

     

    Thorn

     

     

  • thornade_91981's avatar
    thornade_91981
    Icon for Nimbostratus rankNimbostratus
    Mar 25, 2009
    Hi,

     

     

    I have just test with src_addr persistence profile with "Mirror persistence" in both active/active and active/standby mode and I still have the same result : no mirrored records on the standby unit.

     

    I have force the failover standby on first active unit and persistence is lost.

     

    Any idea ?

     

     

    I'm running BIG-IP 9.4.6 Build 401.0 Final on both unit.

     

     

    Thorn

     

  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Mar 25, 2009
    Hi Thorn,

     

     

    I'd suggest opening a case with F5 Support on this. I'm not sure how persistence mirroring should work with an Active-Active configuration.

     

     

    From a functionality standpoint, I'd think you could use cookie insert persistence where the client holds/presents the persistence information. No data is stored on LTM, so you wouldn't need to worry about mirroring the persistence record. I understand that this isn't what you're testing, but figured I'd throw it out there as an option.

     

     

    Aaron