--On Tuesday, July 21, 2009 10:48 PM -0400 John Morrissey jwm@horde.net wrote:
On Tue, Jul 21, 2009 at 01:54:25PM -0700, Quanah Gibson-Mount wrote:
--On Tuesday, July 21, 2009 4:51 PM -0400 "Clowser, Jeff" jeff_clowser@fanniemae.com wrote:
Do you have any facts/numbers to back this up? I've never seen F5's slow things down noticably.
We've had F5's be the root of the problem with several clients who load balanced their LDAP servers, and pointed postfix at the F5 for delivery. They added just a few milliseconds of time to each LDAP query, but that was enough to completely back up their mail delivery system. Removing the F5 from the picture allowed mail to flow smoothly, no more problems.
I can't speak for any other clients that Quanah may be referencing, but we experienced this with our Zimbra deployment. However, I emphatically disagree with his stance against running LDAP services behind a hardware load balancer.
Eh, it was against running it behind an F5, not a stance against load balancing in general. ;)
I'm not sure if Quanah heard the final resolution, which was to change the LDAP VIP type from Standard to "Performance (Layer 4)." This solved the problem immediately. I didn't see the final response from F5, but my impression was that Performance (Layer 4) bypasses a lot of the hooks that let you manipulate packets and connections. Interestingly, CPU consumption on our BigIPs was low and therefore didn't prompt us to troubleshoot from that angle. This was the first we've seen this behavior; our non-Zimbra OpenLDAP nodes have a higher operation rate (~12k operations/sec aggregate) and had been servicing a similar mail infrastructure before we started moving to Zimbra's software.
Nope, I wasn't aware of this eventual solution. The last I heard, the postfix part was load balancing against the LDAP urls. So it sounds like F5's can be just fine with that caveat. ;)
--Quanah
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Quanah Gibson-Mount Principal Software Engineer Zimbra, Inc -------------------- Zimbra :: the leader in open source messaging and collaboration