Table of Contents
This appendix is for users who upgrade from earlier DRBD versions to DRBD 8.4. It highlights some important changes to DRBD’s configuration and behavior.
Volumes are a new concept in DRBD 8.4. Prior to 8.4, every resource had only one block device associated with it, thus there was a one-to-one relationship between DRBD devices and resources. Since 8.4, multiple volumes (each corresponding to one block device) may share a single replication connection, which in turn corresponds to a single resource.
The DRBD udev integration scripts manage symlinks pointing to
individual block device nodes. These exist in the /dev/drbd/by-res
and /dev/drbd/by-disk
directories.
In DRBD 8.3 and earlier, links in /dev/drbd/by-disk
point to single
block devices:
udev managed DRBD symlinks in DRBD 8.3 and earlier.
lrwxrwxrwx 1 root root 11 2011-05-19 11:46 /dev/drbd/by-res/home -> ../../drbd0 lrwxrwxrwx 1 root root 11 2011-05-19 11:46 /dev/drbd/by-res/data -> ../../drbd1 lrwxrwxrwx 1 root root 11 2011-05-19 11:46 /dev/drbd/by-res/nfs-root -> ../../drbd2
In DRBD 8.4, since a single resource may correspond to multiple
volumes, /dev/drbd/by-res/<resource>
becomes a directory,
containing symlinks pointing to individual volumes:
udev managed DRBD symlinks in DRBD 8.4.
lrwxrwxrwx 1 root root 11 2011-07-04 09:22 /dev/drbd/by-res/home/0 -> ../../drbd0 lrwxrwxrwx 1 root root 11 2011-07-04 09:22 /dev/drbd/by-res/data/0 -> ../../drbd1 lrwxrwxrwx 1 root root 11 2011-07-04 09:22 /dev/drbd/by-res/nfs-root/0 -> ../../drbd2 lrwxrwxrwx 1 root root 11 2011-07-04 09:22 /dev/drbd/by-res/nfs-root/1 -> ../../drbd3
Configurations where filesystems are referred to by symlink must be
updated when moving to DRBD 8.4, usually by simply appending /0
to
the symlink path.