Dovecot Replication - Architecture Endianness?

[Reuben Farrelly]

Hi all,

I've had an interesting use case come up which - to cut the story short 
- one way to solve the problem I am looking at may be to replicate a 
small number of mailboxes to a third remote server.

I've currently had replication running between my main dovecot machine 
and another remote VM for some time and working well (so I'm not new to 
replication and I've got a good working config), but I've a need to add 
a third to the mix for a select number of mailboxes.  The arch on both 
of those is Gentoo x86_64 and with latest 2.1.16 -hg.

I have attempted this so far by rsync'ing the initial Maildirs and then 
once the bulk of the data has been transferred rely on dovecot's 
replication to keep things in sync.  I figure that this should in theory 
mean that the subsequent updates in both directions are incremental and 
the bulk of the data gets moved while the device is here on my desk 
using rsync.

I've attempted to do this using a Raspberry Pi as a remote device, but 
when I set it up the dovecot replication process seems to need to start 
the replication over from scratch even after the rsync is done.  I know 
this is happening as the disk utilisation on the Pi skyrockets once the 
replication starts and I end up with thousands of double ups of all the 
mails ...  which defeats the entire point of the process.

If I do an identical configuration but on a third Gentoo x86_64 VM 
locally it all works as expected.  No double ups of mails and the 
"catchup" between the two devices is practically instant.  Same 
filesystem even.  The only difference appears to be the system architecture.

So main my question is this.  Is there a known architecture/endian 
limitation on replication?   I guess cross-arch replication is not 
something many people try but is it supposed to work anyway?

Has anyone else got replication working across different arch's?

Also is there a way to restrict replication users aside from a crude 
hack around system first and last UIDs?

Thanks,
Reuben