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author | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-06-18 11:47:10 -0300 |
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committer | Mauro Carvalho Chehab <mchehab+samsung@kernel.org> | 2019-07-15 11:03:01 -0300 |
commit | e7751617dd0599ceadf4221cb08e04307b00aa1f (patch) | |
tree | 16b7a5858f6b4c641e3346e2438f83df49ababa7 /Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst | |
parent | 330d48105245abfb8c9ca491dc53ea500657217a (diff) |
docs: blockdev: add it to the admin-guide
The blockdev book basically contains user-faced documentation.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Diffstat (limited to 'Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst')
-rw-r--r-- | Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst b/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst new file mode 100644 index 000000000000..66036b901644 --- /dev/null +++ b/Documentation/admin-guide/blockdev/drbd/data-structure-v9.rst @@ -0,0 +1,42 @@ +================================ +kernel data structure for DRBD-9 +================================ + +This describes the in kernel data structure for DRBD-9. Starting with +Linux v3.14 we are reorganizing DRBD to use this data structure. + +Basic Data Structure +==================== + +A node has a number of DRBD resources. Each such resource has a number of +devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD +device is represented by a block device locally. + +The DRBD objects are interconnected to form a matrix as depicted below; a +drbd_peer_device object sits at each intersection between a drbd_device and a +drbd_connection:: + + /--------------+---------------+.....+---------------\ + | resource | device | | device | + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + +--------------+---------------+.....+---------------+ + : : : : : + : : : : : + +--------------+---------------+.....+---------------+ + | connection | peer_device | | peer_device | + \--------------+---------------+.....+---------------/ + +In this table, horizontally, devices can be accessed from resources by their +volume number. Likewise, peer_devices can be accessed from connections by +their volume number. Objects in the vertical direction are connected by double +linked lists. There are back pointers from peer_devices to their connections a +devices, and from connections and devices to their resource. + +All resources are in the drbd_resources double-linked list. In addition, all +devices can be accessed by their minor device number via the drbd_devices idr. + +The drbd_resource, drbd_connection, and drbd_device objects are reference +counted. The peer_device objects only serve to establish the links between +devices and connections; their lifetime is determined by the lifetime of the +device and connection which they reference. |