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Re: [LUG] Q for the server builders

 

Hi Gordon,

Quoting Gordon Henderson <gordon+dcglug@xxxxxxxxxx>:

>
> So I'm putting together a small "High Availability" setup for a client
> for a project they're running. It's a LAMPy type of server, so nothing
> special there and it'll be 2 servers running MySQL replication and
> Linux HA between then - again, nothing special there.

A few hints on this - store the PHP sessions in the MySQL database,  
this allows you to install joomla and the like on a cluster without  
worrying about sessions.  If you're using multiple vhosts, storing the  
apache access logs in the database gives you hugely powerful  
data-mining possibilities.  Email me off-list if you want more info on  
these.

> But one thing I'm pondering over - 2 disks in each server or just one?
>
> Now this client is on a bit of a budget here and although disks   
> aren't that expensive, we could spend the £130 or so elsewhere (1TB   
> in each box and WDC drives are in the £60 range now)
>
> The server is going to the co-lo which is 4-5 hours away and normally
> I'd not think twice about using 2 drives per server running in RAID-1
> (mirror) mode, but 2 servers gives us 2 drives...

4 disks minimum IMHO, two in each server configured as RAID-1.  If you  
can afford it (although seeing the budget I suspect not!) 6 disks in  
each server, RAID-5 mirrored as RAID-1 (is this RAID-6 or RAID-15? I  
can never remember and I don't trust Wikipedia any more!).

There's even a part of my nowadays that would design a HA Cluster  
using SAN or NAS as the storage backend and remove all storage  
requirements from the servers.  It also has the added benefits of  
allowing you to add extra nodes to the cluster without worrying about  
replicating the data, just mount the SAN/NAS share in the appropriate  
place.

Hope this of some help,

Matt.

-- 
Matthew Macdonald-Wallace
matthew@xxxxxxxxxxxxxxxxxxxxx
http://www.truthisfreedom.org.uk/

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