[Gllug] best way to update a single production server?

[James Hawtin]

On Tue, May 05, 2009 at 10:52:08AM +0100, Khusro Jaleel wrote:
> Thanks, guys, for all your feedback.
> 
> I assume, then, that if you have 2 web servers with failover (Xen,
> LVS, firewall, whatever), then if you need to do a little DB storage,
> let's say a simple User Guestbook, etc then it's best to put the DB on
> another server, isn't it, or a NAS, etc? This is assuming a web server
> that is 99% read-only, with only the occasional DB access.
> 
> Can you guys recommend a good NAS for this purpose, if that is a good solution?
> 
> I know DB mirroring between the 2 servers that are running in tandem
> can be setup, but I don't think it would work as reliably? I know
> sometimes you need to promote DB slaves to masters before they will
> work?
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One solution I like, is xen and a san, if you get a san with redundancy,
dual controllers, power supplies etc, that ticks to failure resistant
box. Now for "servers" you have at least 2 xen servers present the storage
from the san, then you can to live migration between your xen servers, so if
you need to take one out of service you can move the guests to the other, if
you need to update a guest you can clone it, do updates on a copy while
still running the orginal. You can scale this with as many servers as you
like, this way you don't need 2 servers for every machine just N+1.

James

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