Info on clustering and HAMMER

[Francois Tigeot]

On Thu, Dec 30, 2010 at 08:54:26AM -0500, Francisco Reyes wrote:
> 
> I believe right now Hammer is able to replicate to a second machine in a 
> master slave mode. However the only docs I have seen for data replication is
> http://www.dragonflybsd.org/docs/how_to_implement_hammer_pseudo_file_system_ 
> _40___pfs___41___slave_mirroring_from_pfs_master/
> 
> Hopefully, others can add more info.

hammer's manual page is more complete:

http://leaf.dragonflybsd.org/cgi/web-man?command=hammer&section=8

I'm using the mirror-stream feature to do a pseudo-real-time backup of a
remote imap server.

hammer uses ssh for the transport. You have to do some initial key setup
to allow the backup machine to connect without trying to use passwords
and then it's as simple as that:

  hammer -b 100k mirror-stream root at bigserver:/home backup.bigserv-home

This command synchronizes a local slave filesystem from the /home fs of
bigserver. Since the backup machine is behind a small ADSL line, the
bandwidth used is capped to 100 KB per second.

The remote machine may crash and burn, I'll still have a good copy of
its important data, up to the last few in-flight transactions.

This stuff beats periodic backup schemes hands-down.

-- 
Francois Tigeot