Commit c12adead authored by Andrea Spadaccini's avatar Andrea Spadaccini
Browse files

Add DRBD dynamic resync speed params to design doc



* Expand the Name column of the table (for c-delay-target)
* Add the c-* DRBDparameters to the table containing the disk parameters
* Add the unit of measurement in square brackets, when needed
* Document the supported DRBD version, warn about the DRBD version
  needed for barriers and for the dynamic resync speed parameters.
* Add links to some documentation about the dynamic resync speed
  parameters
Signed-off-by: default avatarAndrea Spadaccini <spadaccio@google.com>
Reviewed-by: default avatarIustin Pop <iustin@google.com>
parent a1505857
......@@ -702,57 +702,106 @@ DRBD setups is added to Ganeti.
At JSON level, since the object key has to be a string, the keys can be
encoded via a separator (e.g. slash), or by having two dict levels.
+--------+-------------+-------------------------+---------------------+------+
|Disk |Name |Description |Current status |Type |
|template| | | | |
+========+=============+=========================+=====================+======+
|plain |stripes |How many stripes to use |Configured at |int |
| | |for newly created (plain)|./configure time, not| |
| | |logical voumes |overridable at | |
| | | |runtime | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |data-stripes |How many stripes to use |Same as for |int |
| | |for data volumes |plain/stripes | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |metavg |Default volume group for |Same as the main |string|
| | |the metadata LVs |volume group, | |
| | | |overridable via | |
| | | |'metavg' key | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |meta-stripes |How many stripes to use |Same as for lvm |int |
| | |for meta volumes |'stripes', suboptimal| |
| | | |as the meta LVs are | |
| | | |small | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |disk-barriers|What kind of barriers to |Either all enabled or|string|
| | |*disable* for disks; |all disabled, per | |
| | |either "n" or a string |./configure time | |
| | |containing a subset of |option | |
| | |"bfd" | | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |meta-barriers|Whether to disable or not|Handled together with|bool |
| | |the barriers for the meta|disk-barriers | |
| | |volume | | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |resync-rate |The (static) resync rate |Hardcoded in |int |
| | |for drbd, when using the |constants.py, not | |
| | |static syncer, in MiB/s |changeable via Ganeti| |
+--------+-------------+-------------------------+---------------------+------+
|drbd |disk-custom |Free-form string that |Not supported |string|
| | |will be appended to the | | |
| | |drbdsetup disk command | | |
| | |line, for custom options | | |
| | |not supported by Ganeti | | |
| | |itself | | |
+--------+-------------+-------------------------+---------------------+------+
|drbd |net-custom |Free-form string for |Not supported |string|
| | |custom net setup options | | |
+--------+-------------+-------------------------+---------------------+------+
Note that the DRBD parameters might change once Ganeti supports DRBD 8.4, in
which the :command:`drbdsetup` syntax has changed significantly.
Moreover, new parameters for the dynamic synchronization algorithm will
be added for DRBD versions >= 8.3.9.
When needed, the unit of measurement is expressed inside square
brackets.
+--------+--------------+-------------------------+---------------------+------+
|Disk |Name |Description |Current status |Type |
|template| | | | |
+========+==============+=========================+=====================+======+
|plain |stripes |How many stripes to use |Configured at |int |
| | |for newly created (plain)|./configure time, not| |
| | |logical voumes |overridable at | |
| | | |runtime | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |data-stripes |How many stripes to use |Same as for |int |
| | |for data volumes |plain/stripes | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |metavg |Default volume group for |Same as the main |string|
| | |the metadata LVs |volume group, | |
| | | |overridable via | |
| | | |'metavg' key | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |meta-stripes |How many stripes to use |Same as for lvm |int |
| | |for meta volumes |'stripes', suboptimal| |
| | | |as the meta LVs are | |
| | | |small | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |disk-barriers |What kind of barriers to |Either all enabled or|string|
| | |*disable* for disks; |all disabled, per | |
| | |either "n" or a string |./configure time | |
| | |containing a subset of |option | |
| | |"bfd" | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |meta-barriers |Whether to disable or not|Handled together with|bool |
| | |the barriers for the meta|disk-barriers | |
| | |volume | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |resync-rate |The (static) resync rate |Hardcoded in |int |
| | |for drbd, when using the |constants.py, not | |
| | |static syncer, in KiB/s |changeable via Ganeti| |
+--------+--------------+-------------------------+---------------------+------+
|drbd |c-plan-ahead |Agility factor of the |Not supported. |int |
| | |dynamic resync speed | | |
| | |controller. (the higher, | | |
| | |the slower the algorithm | | |
| | |will adapt the resync | | |
| | |speed). A value of 0 | | |
| | |(that is the default) | | |
| | |disables the controller | | |
| | |[ds] | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |c-fill-target |Maximum amount of |Not supported. |int |
| | |in-flight resync data | | |
| | |for the dynamic resync | | |
| | |speed controller | | |
| | |[sectors] | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |c-delay-target|Maximum estimated peer |Not supported. |int |
| | |response latency for the | | |
| | |dynamic resync speed | | |
| | |controller [ds] | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |c-max-rate |Upper bound on resync |Not supported. |int |
| | |speed for the dynamic | | |
| | |resync speed controller | | |
| | |[KiB/s] | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |c-min-rate |Minimum resync speed for |Not supported. |int |
| | |the dynamic resync speed | | |
| | |controller [KiB/s] | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |disk-custom |Free-form string that |Not supported |string|
| | |will be appended to the | | |
| | |drbdsetup disk command | | |
| | |line, for custom options | | |
| | |not supported by Ganeti | | |
| | |itself | | |
+--------+--------------+-------------------------+---------------------+------+
|drbd |net-custom |Free-form string for |Not supported |string|
| | |custom net setup options | | |
+--------+--------------+-------------------------+---------------------+------+
Currently Ganeti supports only DRBD 8.0.x, 8.2.x, 8.3.x. It will refuse
to work with DRBD 8.4 since the :command:`drbdsetup` syntax has changed
significantly.
The barriers-related parameters have been introduced in different DRBD
versions; please make sure that your version supports all the barrier
parameters that you pass to Ganeti. Any version later than 8.3.0
implements all of them.
The minimum DRBD version for using the dynamic resync speed controller
is 8.3.9, since previous versions implement different parameters.
A more detailed discussion of the dynamic resync speed controller
parameters is outside the scope of the present document. Please refer to
the ``drbdsetup`` man page
(`8.3 <http://www.drbd.org/users-guide-8.3/re-drbdsetup.html>`_ and
`8.4 <http://www.drbd.org/users-guide/re-drbdsetup.html>`_). An
interesting discussion about them can also be found in a
`drbd-user mailing list post
<http://lists.linbit.com/pipermail/drbd-user/2011-August/016739.html>`_.
All the above parameters are at cluster and node group level; as in
other parts of the code, the intention is that all nodes in a node group
......
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