Redundant web servers.

Dennis devel at muhlesteins.com
Fri Sep 14 15:00:15 MDT 2007


Hi All,

Well, for the past few years I've had a number of servers that host 
another number of websites.  Some are in PHP, some are Python, there is 
even some Java in there.  I've never claimed to know lots about server 
administration so I thought I better run this all past the list.

I've got two sites that need to have a little higher 
availability/redundancy etc.  I've been using Xen across 4 servers to 
host our sites but there isn't enough RAM to host two copies of all the 
virtual servers I've created.  (Like one copy of each server on separate 
hardware for redundancy in case one dies.)  One thing I like about Xen 
is that different servers with different dependencies don't have to have 
lots of customization.  Each one only has what it needs installed.  Xen 
has also worked great for making backups of specific servers and 
restoring or migrating them to different machines when we've had various 
hardware issues over the years. We may be outgrowing it however.

So that's what I wanted feedback on.

I'd like to create an array of servers as described here:
http://www.ibm.com/developerworks/linux/library/l-linux-ha/index.html

What do you guys think would be best:

1) Combine services (web sites) into the same virtual servers, so one 
group of servers hosts all the web sites.  (Like have one cluster of 4 
servers).  In this case, I'd have apache virtual servers, LVS virtual 
servers and perhaps a couple other virtual servers for sites that didn't 
need as much availability or something.

2) Ditch the virtual servers all together and install all the services 
on all the physical machines.  Each machine would have an LVS-ha 
director that manages the IP and could load balance between the 4 
machines for content. 

3) Something I haven't thought of?

Thanks all for any thoughts.
Dennis




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