NFS vs Replication

[David Pottage]

On 2020-07-15 17:33, Andrea Gabellini wrote:
> Hello list,
> 
> I built an email system using a proxy / director pair (IMAP, POP3, 
> LMTP)
> and a backend pair.
> 
> To have an HA system, I would like to understand if it is better to use
> an NFS export or replication to save emails and index files
> 
> NFS is provided by a NAS (in HA), while for replication I would use the
> local backend disks
> 
> Which of the two systems is more reliable? Are there any drawbacks for
> one or the other?

Another option to consider is DRBD replication of the disks at the block 
level.

Despite what you might expect, performance and latency is quite good. A 
number of years ago I ran such a setup hosting a high traffic MySQL 
database, and it worked well. The disks where the limiting factor, not 
the network. In my case the two servers where directly connected by one 
cable without using a switch or suchlike.

One thing to be aware of with DRBD is that the slave disk is not 
accessible at all until you trigger a fail-over, so you can't use it for 
read traffic.

-- 
David Pottage