[CentOS] Load balancing...

[Tim Dunphy]

also I forgot to mention for heartbeat I use keepalived

http://www.keepalived.org/

I found hearbeat a little difficult to implement but keepalived by
comparison is a breeze to setup.  Forget about multiple A records.
That's a naive approach and entirely unnecessary. As other's have
pointed out just setup a virtual ip using keepalived (or heartbeat or
maybe something similar) and point your A record to that virtual ip.

On Fri, Mar 4, 2011 at 11:17 AM, Tim Dunphy <bluethundr at gmail.com> wrote:
>>OK, so what's good?  For my requirements, HAProxy is excellent.  It
>> handled sticky sessions well, performs monitoring of each host, allows
>> dynamic adding/removing of servers, as well as maintenance modes.
>> It's very easy to install and configure.  I'm using is as the backend
>> to apache that is acting as an SSL termination point.  It's been very
>> high performing for us and I know a lot of big sites use it as well.
>> The only question I would have with it is handling of video, as we
>> only use it for typical web traffic, just high bandwidth stuff like
>> that.
>
>> Also, make sure any load balancer you have is redundant and has some
>> kind of failover, using something like pacemaker, heartbeat, etc...
>
> I second the vote for HAProxy. It's one excellent free (as in beer)
> load balancer that is very easy to setup and configure.
>
> One big site that uses it is 37 signals (the makers of basecamp and
> campfire among other things). HAProxy is capable of handling a lot of
> traffic apparently. I use it with a shared docroot living on and NFS
> mount. Works really great! It balances two centos vm's as primary with
> a physical freebsd host acting as a fallback.
>
> Other good choices include nginx with the upstream fair plugin and
> #pound from apsis.
>
> http://www.apsis.ch/pound/
> http://wiki.nginx.org/LoadBalanceExample
>
> Any of the above (pound, nginx or haproxy) will handle sticky sessions
> skillfully.
>
>
> As to hardware load balancers I think that Netscaler by citrix
> deserves an honorable mention:
>
>
> http://deliver.citrix.com/go/citrix/WWAD0111Q1NSGOOGLECLOUDWP?gclid=CNDzzIantacCFQFM5QodslJN_w
>
> But like any hardware lb they're certainly not cheap!! I remember when
> my last company was considering which load balancer to go with the
> contenders were Zeus, F5 and Citrix Netscaler.
>
> I think they're all good products, but I remember when the F5 salesman
> came by, part of his sales pitch was "Ok, if you don't go with us I
> can understand why you would go with Netscaler. But Zeus? Really,
> guys?"
>
>
>
> On Fri, Mar 4, 2011 at 10:09 AM, Brian Mathis <brian.mathis at gmail.com> wrote:
>> On Thu, Mar 3, 2011 at 6:43 PM, Todd <slackmoehrle.lists at gmail.com> wrote:
>>> Hi All,
>>> Can anyone help me hash out how best to load balance a website that is
>>> getting considerable traffic?  In the past I only have experience with BigIP
>>> where you have a load balancing device that keeps track and send traffic to
>>> the best server possible at the time. This was a proprietary system that I
>>> think was something Dell rebranded.
>>> Right now, the whole site is is 400gb of video, HTML5, Apache, PHP, MySQL,
>>> runs on a single box with 16gb of RAM and mirrored /var/www/html (2x1tb raid
>>> level drives). I have a Comcast 50/10 connection, 5 statics and I am seeing
>>> about 125 unique visitors a day. The site runs fine, but in anticipation of
>>> more traffic as well as a learning experience I would like to load balance.
>>> Obviously I need a second server just like the one it is running on now. I
>>> will probably spec something out that is capable of 32gb of RAM.
>>> What about a dedicated load balancing device? What specs should this be? How
>>> much RAM, HD, processor? It is sufficient to buy something with a GB NIC and
>>> say 4gb of RAM? Can one go slower but more RAM, small HD?  I don't really
>>> quite know how intensive a task this decision making process is for the load
>>> balancer..
>>> Right now, as example, I have an Untangle Firewall and it runs on a old AMD
>>> with 2gb RAM, GB NIC and it seems to do just fine.
>>> My local computer store has several P4 2.8ghz with 2GB of RAM for like
>>> $99....
>>> Can anyone enlighten me on specs, proper setup, caveats....?
>>> -Jason
>>
>>
>> You have a lot of issues here, and some unanswered questions.  Is the
>> load on your site mostly bandwidth use?  Do you have users who need to
>> login to a system?  Is the application designed to run with multiple
>> front-ends?  It's easy to get very basic load balancing, but your app
>> most likely will require "sticky sessions" to ensure the user goes to
>> the same backend server every time, and many solutions don't have this
>> feature.
>>
>> Of the free options already listed, here are the problems with them:
>> - Round Robin DNS:  Provides no additional features other then very
>> poor "load spreading" across servers.  As soon as you talk about load
>> balancing there are usually features you need that this cannot
>> provide, like automatic failover, dynamic adding/removing hosts,
>> etc...  Sticky sessions are simply not possible.  RR DNS should not be
>> used except in extremely basic situations.
>>
>> - Linux LVS:  This is a good idea on the face of it, but it can open
>> up some tricky issues with routing and IP address handling.  Also,
>> sticky sessions are based on subnet of the IP address, which for many
>> corporations using proxies will not work.  I have seen companies that
>> spread their proxy load across multiple /8 networks, so there's no way
>> to sticky them.
>>
>>
>> OK, so what's good?  For my requirements, HAProxy is excellent.  It
>> handled sticky sessions well, performs monitoring of each host, allows
>> dynamic adding/removing of servers, as well as maintenance modes.
>> It's very easy to install and configure.  I'm using is as the backend
>> to apache that is acting as an SSL termination point.  It's been very
>> high performing for us and I know a lot of big sites use it as well.
>> The only question I would have with it is handling of video, as we
>> only use it for typical web traffic, just high bandwidth stuff like
>> that.
>>
>> Also, make sure any load balancer you have is redundant and has some
>> kind of failover, using something like pacemaker, heartbeat, etc...
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>> http://lists.centos.org/mailman/listinfo/centos
>>
>
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