ACE - backup serverfarm (sticky-serverfarm)

Unanswered Question
Jul 31st, 2008

Hi !

I did a sticky-serverfarm configuration. What I would like to achieve is to have a backup-path if the main serverfarm is out-of-service.

I saw the additional "backup" command within a normal serverfarm config - but within a sticky-serverfarm this backup command is not available.

Can you please tell me how to configure a backup serverfarm within a sticky serverfarm ?

thx

Hans

I have this problem too.
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sachinga.hcl Thu, 07/31/2008 - 04:59

Hi Hans,

you can use the sticky-serverfarm inside a class map and then add this class map inside a policy map.

for example

old config

Create a sticky-group

sticky ip-netmask 255.255.255.255 address source ep-sourceIP-sticky

timeout 10

serverfarm ep backup ep-backup aggregate-state

•Change the server farm to the sticky-group:

New Config (suggested)

policy-map type loadbalance first-match basic-slb

class class-default

sticky-serverfarm ep-sourceIP-sticky

Note that the backup statements have moved from the load balance policy map configuration to the sticky-group configuration.

Best regards

sachin garg

Syed Iftekhar Ahmed Thu, 07/31/2008 - 10:01

If your primary serverfarm is APP1-SF1 & Backup serverfarm is APP1-SF2

you need to configure....

sticky ip-netmask 255.255.255.255 address source APP1-sticky

timeout 60

serverfarm APP1-SF1 backup App1-SF2

Syed Iftekhar Ahmed

huangedmc Thu, 07/31/2008 - 14:43

Syed's config is exactly how we're doing it, and it works.

However, if you're running A1 train, user sessions are stuck to the backup farm, even when the primary farm comes back up.

The A2 train of code resolves that flaw.

As long as you don't have the "sticky" option after the backup farm under sticky config, the backupfarm is not sticky.

We have not upgraded to A2 train, so can't confirm if it actually works, but that's what TAC told me, and the config doc for A2 indicates such as well.

schimeha1977 Sun, 08/03/2008 - 23:12

Hi !

Many thanks for your help !!!

May I ask you another question ?

Is it possible to configure this sticky/backup serverfarm - with a condition like: if 50% of the sticky serverfarm fails then switch to the Backup ..

??

thx

Hans

Syed Iftekhar Ahmed Mon, 08/04/2008 - 08:23

Partial Serverfarm failover feature in ACE 2.x code can do that

You can enable partial server farm failover by using the partial-threshold command in server farm host configuration mode. The syntax of this command is as follows:

partial-threshold number1 back-inservice number2

•number1-Minimum percentage of real servers in the primary server farm that must remain active for the server farm to stay up. If the percentage of active real servers falls below this threshold, the ACE takes the server farm out of service. Enter an integer from 0 to 99. The default is 0.

•back-inservice number1-Specifies the minimum percentage of real servers in the primary server farm that must be active again for the ACE to place the server farm back in service. Enter an integer from 0 to 99. The value that you configure for the back-inservice keyword must be greater than or equal to the partial-threshold value. The default is 0.

For example, to configure a partial server farm failover, enter:

host1/Admin(config)# serverfarm host SF1

host1/Admin(config-sfarm-host)# partial-threshold 40 back-inservice 60

More details at

http://www.cisco.com/en/US/docs/interfaces_modules/services_modules/ace/v3.00_A2/configuration/slb/guide/rsfarms.html#wp1000206

Syed Iftekhar Ahmed

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