On 11/04/2014 06:15 PM, Anton Aylward wrote:
On 11/04/2014 06:53 PM, John Andersen wrote:
While installing 13.2 I let it use btrfs for root and xfs for /home partition.
Then you get these nebulous message that says some of the subvolumes of root are shadowed by other filesystems. That message means that you have a subvolume named /home defined in the /root automatically, and also a /home partition. Better language is needed for that error message. The term "Duplicate directory" names comes to mind. "Shadowed" is not very descriptive.
But then I began to wonder why btrfs defines subvolumes instead of letting the system define sub-directories?
Whats the difference in functionality? Are these sub-volume sizes fixed? Is it just part of the snapshot process? What's up with that?
I'm sure the designers had something in mind and its quite possibly documented somewhere. What follows is my thoughts and experience.
I did the installation as you described. Eventually the /home partition corrupted irretrievably. Its not a conventional reiserFS restored from a backup.
I think that the BtrFs model is that the FS should encompass the whole of the system as one logical volume possibly across many partitions or platters or spindles. It has that capability.
The subvolume mechanism, the manual says, can be treated like a directory or a moutned FS. Perhaps that's what is confusing about it. You can have a real (as in the XFS) mounted on /home or or ....
Well, in any other other FS if you don't mount the partition on /home you can still create stuff there, and when you do the actual mount it does overlay. "shadowed". So I asked myself why bother and cleared out all the subvolumes.
OUCH! That mean that /usr got DELETED. The subvolumes are not just markers. They really are directories.
Or are they? See https://lwn.net/Articles/579009/
*sigh* Re-install. "Learning experience".
This time I did without subvolumes and I can't say i missed them.
I'm sure that the idea behind BtrFS is that it can optimise the btree and space in some fantastic way. I'm sure that it really wants the whole of my 1T drive to be the BtrFS, including /boot and /swap. And I'm sure it can mirror onto another, and I'm sure that the subvolumes can be snapshotted and can then be used for a disk-to-disk-to-tape backup. I'm certain that just as my LVM partitions can grow and grow across spindles, so can BtrFS.
I am not, however, ready, to try installing a system on a single, encompassing single BtrFS. I'll let someone else try it and report. I'll also let someone else experiment with that BtrFS growing across many spindles.
https://btrfs.wiki.kernel.org/index.php/Main_Page
What I might experiment with, though, is this
<quote src="http://www.oracle.com/technetwork/articles/servers-storage-admin/advanced-btrfs-1734952.html"> Redundant Configuration
With Btrfs, you no longer need to use mdadm to create mirrored volumes or complex RAID configurations. These capabilities are built into the file system. </quote>
What I'm not clear on is how to extend an existing FS to become a BtrFS style RAIDFS.
All very interesting reading. The first link especially is a nice gentle introduction to the concepts. And looking at my mtab I can see it did indeed mount all those sub-volumes separately. /dev/sda2 /.snapshots btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/tmp btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/spool btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/opt btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/log btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/lib/named btrfs rw,relatime,space_cache 0 0 /dev/sda2 /boot/grub2/x86_64-efi btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/crash btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/lib/pgsql btrfs rw,relatime,space_cache 0 0 /dev/sda2 /usr/local btrfs rw,relatime,space_cache 0 0 /dev/sda2 /var/lib/mailman btrfs rw,relatime,space_cache 0 0 /dev/sda2 /tmp btrfs rw,relatime,space_cache 0 0 /dev/sda2 /srv btrfs rw,relatime,space_cache 0 0 /dev/sda2 /opt btrfs rw,relatime,space_cache 0 0 /dev/sda2 /boot/grub2/i386-pc btrfs rw,relatime,space_cache 0 0 Some of those mounts are two levels deep in the file tree! I've got a bit of studying to do. For now I'm using it more or less as the default install. I did a fresh install because I needed to repartition my disk anyway. Since I have a fresh backup from before, I am also trying encrypted volumes. It didn't want to let me encrypt a btrfs partition where I store my source code so I had to forgo the snapshot capabilities and use XFS for that partition. -- Explain again the part about rm -rf / -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org