HAMMER snapshot and mirror vs ZFS snapshot and clone

Matthew Dillon dillon at backplane.com
Sat Dec 27 10:21:41 PST 2014


HAMMER has a built-in history but it also has to be able to clean it up to
recover space.  The snapshots are basically a list of transaction ids that
the clean-up code cannot cross when combining history entries together.

Hammer's mirror-stream is a way to mirror a master onto a read-only slave
in real time.

-Matt


On Thu, Dec 25, 2014 at 9:14 PM, Predrag Punosevac <punosevac72 at gmail.com>
wrote:

> Could a kind soul point me to the additional documentation besides
> man hammer(5) and man hammer(8) which will help me further understand
> the difference in use/purpose of HAMMER snapshot and
> mirror-copy/mirror-stream on the production file server? I am also
> interested to hear from gurus what is the main difference of HAMMER
> snapshot vs ZFS snapshot and also how does mirror-copy/mirror-stream
> compares to ZFS clone.
>
> My confusion in part comes from the fact that HAMMER has build in
> history which is non-existing on ZFS so it seems that snapshots are kind
> semi-redundant if the history is enabled. Of course history might be
> very expensive in terms of disk space as I learned hard way about half a
> year ago so turning off history and taking HAMMER snapshots instead
> might be desirable in some situations.
>
> Could anybody point me to any examples of mirror-stream via ssh to a
> remote machine. Is there a way to encrypt mirror-stream on the fly when
> doing it to a remote location?
>
> Most Kind Regards,
> Predrag
>
> P.S. I read serveral times over HAMMER crash course posted on BSD now.
>
>
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