This guide describes DRBD version 8.4 and above. For 8.3 please look here.
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.
This guide describes DRBD version 8.4 and above. For 8.3 please look here.