# HA: statefull failover

## highland

Hello

I have two apache servers on different machines working as active-standby.

What active fails standby takes over active's IP address and start working as active.

What i am looking for is solution for statefull failover - a way to share/synchronize TCP/IP sessions.

On cisco routers i use SCTP protocol for that. Now i would like to implement similar solution on gentoo.

Could you recommend protocol/solution which works on gentoo ?

Thanx

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## highland

i found balanceng - but it is commercial solution - and quite expensive for small company  :Sad: 

it uses VRRP extensions for sessions replication.

So - i am still looking for ANY solution...

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## papahuhn

Is that even possible with two separate Apache instances? I mean, if the active server fails in the middle of a larger download, how should the standby apache know, which resource to deliver?

SCTP itself is available in Linux, though.

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## highland

Standby apache would not guess what resource to deliver in such case - but TCP session would be kept alive,

and the client (web browser) would need to send only GETs for the missing content instead of initiating new TCP session(s)

which is done automatically by the web browsers.

In case we do not have failover TCP session is broken and browsers might have problems with initiating new TCP sessions.

I prefer failover then load-balancer - because load-balancers are still single point of failure (and we need failover for load-balancers)

so at the end of a day we still need failover mechanism to provide true HA.

SCTP is just transport protocol, we need application protocol/tools which are actually responsible for sending sessions info to standby (and i guess we need kernel module/interface which actually copies that data to standby kernel).

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