dovecot - Oct 2015 - Migrating to new server, questions about recommended configuration.

Hello!  I'm moving Dovecot from a FreeBSD Jail (on ZFS using Maildir) to an
Amazon EC2 Debian host.

1) I was on Dovecot 2.1 on my FreeBSD system but upgraded it to 2.2 so I could
use dsync for the transfers.  Is dsync the best way to migrate my data?

2) On the new Debian host, is there a better filesystem than EXT4 that I should
use for the mail storage?

3) On the new host, is mdbox generally recommended over maildir?  Especially
when mixed with dsync?

4) Does dsync work as a good backup tool to keep a mirror of my live system?

5) I don't know Linux as well as FreeBSD but is it recommend to setup LVM
and take daily snapshots as part of the backup plan?  Do LVM snapshots cause any
problems with Dovecot in the case of a rollback/restore?

Hi,

I can only write about my experience:
> 2) On the new Debian host, is there a better filesystem than EXT4 that I
should use for the mail storage?
I have used ext4 and never had problems with it for ages. Since recent times I
also use ZFS on linux, but it's a bit slower and eats lots of RAM as you
probably know
> 3) On the new host, is mdbox generally recommended over maildir? 
Especially when mixed with dsync?
Generally yes, brings speed a little speed boost, however administration is not
as simple as with maildir (no systemtools like cp, rsync etc; you have to use
dovecots tools); don't know in combination with dsync since I have not used
it except for backup.
 
> 4) Does dsync work as a good backup tool to keep a mirror of my live
system?
yes, so far I have not had any troubles
> 5) I don't know Linux as well as FreeBSD but is it recommend to setup
LVM and take daily snapshots as part of the backup plan?  Do LVM snapshots cause
any problems with Dovecot in the case of a rollback/restore?
Generally, LVM and snapshots are nice. However, We had some troubles with it:
having snapshots will have a significant impact on your performance; we have
also encountered problems with rollbacks where removing snapshots got stuck;
this was one of the reasons why we switched to ZFS (or: we are in process of
switching)

and just for info: my systems are all quite small (<1000 users).

regards,
infoomatic