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Re: [lvs-users] Sync table PIRANHA (DIRECT ROUTING) works only long last

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] Sync table PIRANHA (DIRECT ROUTING) works only long lasting connections
From: "L.S. Keijser" <leon@xxxxxxxx>
Date: Tue, 27 Oct 2009 20:51:36 +0100
On Tue, 2009-10-27 at 13:24 -0200, Raul da Silva {Sp4wn} wrote:
> I heard the following about flow of "master/bakcup" sync (piranha + dr ):
> 
> Once a connection is established, the master sync daemon (on the active
> director) sends data to the backup sync daemon (on the backup director).
> The backup director is then aware of an established connection. If the
> primary director fails, the backup will take over and still forward packets
> from an established connection to the right reral server.
> 
> This works fine on long lasting connections (interactive sessions like FTP,
> telnet, SSH and so on) but doesn't on short connections (http without
> keepalive for example).
> 
> Is it true ? if is true I think the better way to solve this is implement
> some solution like conntrack-tools (netfilter).

I can't test it, because my version of ipvsadm (ipvsadm v1.24 2005/12/10
(compiled with getopt_long and IPVS v1.2.1)) the sync daemons don't work
at all :(  But AFAIK it should work on all connection types.

But you could try to alter the values
in /proc/sys/net/ipv4/vs/sync_threshold.  By default it's set to '3 50'
meaning after 3 packets the connection gets synchronized and each next
50 packets will cause the connection to sync. Try lowering these values
and experiment if this helps you.

You could also see:

http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.server_state_sync_demon.html

which has a piece on piranha and sync daemons.

-- 
Léon


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