> From: Richard Elling [mailto:richard.ell...@gmail.com]
>
> >> What happens when you remove the directory?
> >
> > Same thing that happens when you remove the .zfs directory. You
> can't.
>
> Are you sure I cannot rmdir on a NetApp? That seems like basic
> functionality to me.
>
> Or are you thinking "rmdir dirname/.snapshot" when I'm thinking
> "rmdir dirname; mkdir dirname" which is a common operation
> in a developer environment. Or "mv dirname dirname-old;
> mv dirname-new dirname" which is common when managing
> software upgrades that are not clone-aware.
I don't see what the confusion is.
In ZFS:
cd /tank/home/eharvey
mkdir foo
touch foo/bar
sudo zfs snapshot t...@bestsnapshotever
rm -rf foo
ls /tank/.zfs/snapshot/bestsnapshotever/home/eharvey/foo
bar
In NetApp:
cd /netapp-nfs-mountpoint/home/eharvey
mkdir foo
touch foo/bar
(as root on the netapp) snap create vol0 somesnapshot
(back on my nfs client)
rm foo/bar
ls -l foo/.snapshot/somesnapshot
bar
ls -l .snapshot/somesnapshot/foo
bar
rmdir foo
ls -l foo/.snapshot
foo: No such file or directory
ls -l .snapshot/somesnapshot/foo
bar
Point is, in Data Ontap, *every* directory has a .snapshot subdirectory. If
you rmdir a directory, then you can find that directory in the .snapshot of
its parent.
Does that answer it?
Point is, this way you never have to guess how many filesystems are nested
within higher level zfs filesystems, you never have to guess how far up the
tree you need to go, in order to find the correct .zfs subdirectory which
contains the snapshots for your PWD. It's simply more convenient to use
netapp style .snapshot subdirectories instead. Plus, all my users can
remember ".snapshot" but they don't remember ".zfs" or even worse: "Use the
.zfs, but only at the 3rd level of parent directories, to access snaps for
your home, but go one level higher for the snaps of anything outside your
home directory..."
This is a tiny little point, where netapp is simply better. And I'm sure
there are some other points, but I don't personally care about them as much
as the advantage zfs has over netapp. Namely, installable on normal
hardware, no license fees necessary to snap replicate (zfs send) filesystem
copies all over my world. Snap onto removable disks. Restore using a free
black box, mount it in my laptop, etc etc.
At present, the workaround I have for zfs is:
ln -s .zfs/snapshot snapshot
This makes the snapshot directory plainly visible to all NFS and CIFS users.
Easy to find every time, easy to remember. Especially important for Mac
cifs clients, because there's no addressbar to type in ".zfs" even if you
knew that's what you want to do.
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