[WBEL-users] Custering in WBEL/RHES/AS

[kirby]

Ben,

My experience with clustering has been on Sun, but the principles should
still apply.

There are two levels to the cluster (in my mind).  
The first is you need the hardware; You need to have the disk infrastructure
so that both servers can see the drives.  When we have don this it has been
over fibre, but you can potentially do this over Ethernet as well (NAS
Storage Array vs SAN)
Once you get the structure set-up then you can create the files systems on
those disk and let each server know that it is a shared disk running GFS (or
whatever fs you choose to use that supports multiple server access).

Note:  30 min unplanned downtime is GREAT.  My experience with small
clustered systems is that they cause more problems than they help.  It is
VERY complicated to set-up.  Maintenance becomes a pain.  No one knows how
to support it.  The technology is still bleeding edge.
For a large cluster with sophisticated Unix admins and DBA's it can be good,
but IMO a clustered db is about 3x the work for and extra (maybe) .001%
uptime improvement.  If you are AMEX or VISA it is worth it... For most
others.  I go for KISS.

Steve





--- Benjamin Smith <lists at benjamindsmith.com> wrote:

> Does anybody here have experience with clustering on WBEL/RHES/AS?
> 
> I have a web-based application hosted on WBEL/PostgreSQL and am 
> looking for
> the best way to provide even higher uptimes. (So far, 30 minutes of
unplanned 
> downtime in over a year) 
> 
> I'm having some difficulty fully understanding what GFS is actually 
> all about.
> Is my understanding of GFS such that I could have two machines, each with 
> their own HDD, and have it set up with GFS as a sort of cross-machine
RAID1? 
> 
> If I could save data like this, and then replicate the PostgreSQL 
> database
> with Slony, I *think* I'd have a good solution for redundant servers at
the 
> colo with minimal downtime in the event of a failure of either system...
Am I 
> right? 
> 
> Ideas/thoughts/pointers? Has anybody here set up stuff like that?
> 
> Currently, we have two servers, a "live" server, and a hot backup 
> which
> synchronizes its filesystems periodically to the live server with rsync.
This 
> gives a good "worst case scenario" recovery plan, but doesn't give much 
> support for lighter-grade failures. 
> 
> -Ben