Hi Sebastian, I posted a similar question and got many helpful answers: https://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg35047.html Basically, you cannot guarantee that the computing mounting /dev/sdx doesn't write to arbitrary addresses of /dev/sdxN as unallocated blocks and thus corrupting the file system on it (I assume sdxN in your example is a sub volume of sdx). On Wed, Jul 16, 2014 at 6:18 PM, Sebastian Ochmann <ochmann@xxxxxxxxxxxxxxxxxxxxxx> wrote: > Hello, > > I'm sharing a btrfs-formatted drive between multiple computers and each of > the machines has a separate home directory on that drive. The root of the > drive is mounted at /mnt/tray and the home directory for machine {hostname} > is under /mnt/tray/Homes/{hostname}. Up until now, I have mounted /mnt/tray > like a normal volume and then did an additional bind-mount of > /mnt/tray/Homes/{hostname} to /home. > > Now I have a new drive and wanted to do things a bit more advanced by > creating subvolumes for each of the machines' home directories so that I can > also do independent snapshotting. I guess I could use the bind-mount method > like before but my question is if it is considered safe to do an additional, > "regular" mount of one of the subvolumes to /home instead, like > > mount /dev/sdxN /mnt/tray > mount -o subvol=/Homes/{hostname} /dev/sdxN /home > > When I experimented with such additional mounts of subvolumes of > already-mounted volumes, I noticed that the mount options of the additional > subvolume mount might differ from the "original" mount. For instance, the > root volume might be mounted with "noatime" while the subvolume mount may > have "relatime". > > So my questions are: Is mounting a subvolume of an already mounted volume > considered safe and are there any combinations of possibly conflicting mount > options one should be aware of (compression, autodefrag, cache clearing)? Is > it advisable to use the same mount options for all mounts pointing to the > same physical device? > > Best regards, > Sebastian > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
