DragonFly users List (threaded) for 2010-04
Re: Snapshots ordering on slave and pfs according to freequency for snapshot management
I've been thinking about the issue of mounting snapshots and I
have an idea.
In order for a slave snapshot link to work it must reference the
@@<transactionid>:<pfsid> portion of the softlink relative to the
base HAMMER filesystem the PFS was created in.
You can do this by creating a dummy subdirectory in the base HAMMER
filesystem and then using a nullfs mount to mount that underneath
your samba export hierarchy.
Then you can have snapshot softlinks that push in through there.
You do not have to rename or move the PFS itself.
So, here's an example. Lets say you have:
/samba_export Your samba export hierarchy
/hammer Your hammer filesystem
/hammer/pfs/blah Some PFS in the hammer filesystem
And now lets asy you want to make snapshots from PFS(s) in the hammer
filesystem available to the export. This would work:
mount_null /hammer/pfs /samba_export/fubar
Similarly you can adjust or create snapshot softlinks that are relative
to the samba_export path's null mount and store them somewhere in
/samba_export. In this case you might want to use a different
mount_null /hammer/samba_pfs /samba_export/fubar
And then create the specially formatted hammer PFS softlinks in
ln -s "@@PFS00001" blah
(where the PFS number is formatted as "@@PFS%05d").
There is absolutely nothing preventing you from creating as many
@@PFS%05d softlinks as you want, all pointing to the same PFS. The
only requirement is that they be created inside the HAMMER filesystem
the PFSs were created in.
You may have other issues... tracking the snapshots could present
a problem since hammer cleanup only allows one snapshot directory
to be specified. So you might have to come up with a little script
to maintain a second set of snapsoft softlinks with the proper samba
path which mirrors the master set which hammer cleanup maintains.
Otherwise you will wind up with a lot of stale snapshot softlinks.