high-availability again

Dave McMurtrie dgm+ at pitt.edu
Thu Apr 14 09:01:11 EDT 2005

zorg wrote:

> Hi
> I'v seen in the list lot of discussion about availabity but none of them 
> seem to give a complete answers
> I have been asked to build an high-availability for 5000 users
> I was wondering what is actually the best solution
> Using murder Idon' t really understand if it can help me. it's purpose 
> is for load balancing.

Murder, by itself does not give you high availability.  It does give you 

> but some people on this list seem to use it for availabily like this
> - Server A
>  - active accounts 1-100
>  - replicate accounts 101-200 from Server B
> - Server B
>  - active accounts 101-200
> - replicate accounts 1-100 from Server A
> If B goes down, A takes over the accounts it had
> replicated from B.
> if someone can explain the detail of this conf ?
> - the tool use to replicate ?
> - what configuration of the MUPDATE make it to switch the user to server 
> A from B ??

I'm not familiar with this.

> Replication with rsync
> see to slow the 5000  user

It'd be tough to do this real-time.  We used to have a setup where we'd 
rsync to a standby server each night.  The plan was to use it as a 
warm-standy in case the primary server would happen to fail. 
Fortunately that never happened.

> Cluster with block device
> but if you have a heavily corrupted filesystem. yau are stuck. and 
> recovery can be long

I'm not sure exactly what you mean here, but I think it's safe to say 
that any time you have a corrupted filesystem it's bad whether it's a 
clustered filesystem or not.

> Using a SAN : Connect your two servers to a SAN, and store all of
> Cyrus' data on one LUN, which both servers have access to.  Then, set
> your cluster software to automatically mount the file system before
> starting Cyrus.

We're doing this.  We have a 4-node Veritas cluster with all imap data 
residing on a SAN.  Overall it's working quite well.  We had to make 
some very minor cyrus code changes so it'd get along well with Veritas' 
cluster filesystem.  This setup gives us high availability and scalability.

> but if you have a heavily corrupted filesystem. yau are stuck. and 
> recovery can be long

Again, yes.  It would be bad if we had a corrupt filesystem.


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