[ClusterLabs] DRBD or SAN ?

[Dmitri Maziuk]

On 7/17/2017 4:51 AM, Lentes, Bernd wrote:

> I'm asking myself if a DRBD configuration wouldn't be more redundant and high available.
...
> Is DRBD in conjuction with a database (MySQL or Postgres) possible ?

Have you seen https://github.com/ewwhite/zfs-ha/wiki ? -- I recently 
deployed one and so far it's working better than one centos 7 drbd + 
pacemaker + nfs cluster I have. Although in 20-20 hindsight I wonder if 
I should've gone BSD instead.

If your database is postgres, streaming replication in 9.latest is 
something to consider. I haven't had any problems running it on top of 
drbd, but there are advantages to having two completely independent 
copies of everything. Esp. if it's on top of zfs's advantages.

We already "upgraded" our webserver postgres to streaming replication, 
in the next month or so I plan to bump it to 9.latest from postgres 
repo, run two independent instances, ditch drbd altogether and use 
pacemaker only for floating ip. (And zfs insremental snapshots to 
replicate static content.)

In that scenario freebsd's carp looks like much leaner and cleaner 
alternative to the whole linux ha stack and with zfs in the kernel and 
absence of systemd... the grass on the other side looks greener and 
greener every day.

Dima