hammer-mirror question of hammer1 and hammer2

[Sven Gaerner]

On Sun, May 04, 2014 at 08:31:38AM +0800, lhmwzy wrote:
>     In hammer1,the target of hammer-mirror must be a hammer pfs slave,which
> means that the target can't be mounted and  lived show the source hammer
> pfs master changes.
>     For example,if the hammer pfs master is down,the mirror hammer pfs
> slave will not online automaticly which like a cluster filesystem will do.
> 
>     I read the hammer2 design document and find that hammer2 can do this,am
> I correct?
> 
>     All things I want is hammer-mirror run between many hammer pfs, each
> hammer pfs can be mounted with read (and write) mode while a ongoing
> hammer-mirror.
> 
> Sorry for my bad english.I wish you could understand what I have say.

You can only access a PFS slave in read-only mode. You have to upgrade
(hammer pfs-upgrade) a PFS slave to a PFS master to also allow
read-write access. But then you cannot use mirror-copy to update this
master PFS. The hammer mirror-copy works only from one PFS master to
many PFS slaves.

But you can use mirror-stream to continuously update your PFS slave from
you PFS master, while at least the master is in use.

Automatically replacing a going down PFS master with one of its PFS
slave might be possible, but this will manual work. I don't know if
there is a out-of-the-box solution.

In hammer2 this might change (I did not follow the latest changes in the
development), but AFAIK hammer2 is still under heady development.

Sven