[CentOS] high availability ideas

Sat Nov 19 16:34:40 UTC 2011
Les Mikesell <lesmikesell at gmail.com>

On Sat, Nov 19, 2011 at 5:11 AM,  <nux at li.nux.ro> wrote:
> Thank you, however I decided to go for a less exotic setup and use a more
> passive way of sync (probably rsync and mysql replication) and I'll do
> the high availability part from DNS (yes, I know there are issues with this
> solution as well).

It can be hard to get a client to switch locations by changing a
single IP as your  DNS response because the application may cache much
longer than the TTL, but most web browsers are very good at dealing
with receiving multiple IP addresses where one or more servers in the
list do not respond.  That is, if you always give out 2 IP's but only
one target responds, most browsers will do the right thing most of the
time, and you can improve it by either running both sites live or
making the inactive site do a redirect to a site-specific name for the
active site.   And if you are writing your own client for a service it
is usually much easier to make the client smart enough to find a
working server than to keep a lot of data perfectly synchronized

   Les Mikesell
     lesmikesell at gmail.com