Beginners questions

Justin Sherrill justin at
Wed Dec 4 10:45:55 PST 2013

On Wed, Dec 4, 2013 at 1:03 PM, Cassandra von Ahrcanburg <
proudmouse at> wrote:

> > Keeping the history is also a nice feature that is not available in
> > ZFS. It's sort of built-in backup. This needs some extra space,
> > especially if a lot of files are changed very often.
> This is cold storage, so I would probably deactivate this feature
> anyway - or at least reduce it.

If you'll only ever have one version of the file on disk, history won't
help much, but if there's any chance a user will come up and say, "I
scrambled this one file/set of files/whole directory; can I get yesterday's
version?", it makes it very easy to fix.

a similar example: I managed several times to accidentally delete all the
pkgsrc binaries for a given DragonFly release when trying to sync over a
new build.  12,000 or so packages, gone.  I was able to copy them all back
into place because of Hammer.

> Both. As written before, this is cold storage and things will usually
> not get removed, but instead, the archive will tend to grow. The
> problem is, that I can't really say where. So setting a mount point in
> a good position within the archives directory tree is near to
> impossible. What I have done until now (with UFS) is to give each drive
> a mount point outside of the archive. Beside all of these there is also
> a directory tree (without files) of for the archive. Then I connect the
> last directory level with smylinks to the tree. This way, when I add a
> drive, adding its contents to the tree is a matter of clevis, but in
> terms of skill, rather trivial.

DragonFly's mount_null works quite well, so you can use that to arbitrarily
place drives.  That may or may not make your life less complicated.

> Just to be sure: In this context a volume could be a physical drive. So
> creating a single fs over both ad1 and ad2 is a bad idea. I can
> understand that, because this constellation would be something like a
> RAID0. If one drive dies, all data is lost. If however ad1 and ad2 are
> combined to a single volume either with vinum oder LVM, creating a
> hammer on that would be ok.

I'm pretty sure that is correct - with the caveat that I haven't tried it.
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