HAST + ZFS + NFS + CARP

[Miroslav Lachman]

Julien Cigar wrote on 07/01/2016 12:57:

>>> why...? I guess iSCSI is slower but should be safer than HAST, no?
>>
>> do your testing, please. even with simulated short network cuts. 10-20
>> secs are way enaugh to give you a picture of what is going to happen
>
> of course I'll test everything properly :) I don't have the hardware yet
> so ATM I'm just looking for all the possible "candidates", and I'm
> aware that a redundant storage is not that easy to implement ...
>
> but what solutions do we have? It's either CARP + ZFS + (HAST|iSCSI),
> either zfs send|ssh zfs receive as you suggest (but it's
> not realtime), either a distributed FS (which I avoid like the plague..)

When disaster comes you will need to restart NFS clients in almost all 
cases (with CARP + ZFS + HAST|iSCSI) and you will lose some writes too.
And if something bad happens with your mgmt scripts or network you can 
end up with corrupted ZFS pool on master and slave too - you will need 
to recovery from backups. For example in some split brain scenario when 
both nodes will try to import pool.

With ZFS send & receive you will lose some writes but the chance you 
will corrupt both pools are much lower than in the first case and the 
setup is much simpler and runtime error proof.

I rather prefer some downtime with safe data than shorter downtime but 
data in risk. YMMV

Miroslav Lachman