Thanks for the review. Unfortunately in some design document the style
is broken.
I've fixed all the remarks in the v2 patch.
On 10.07.2015 12:24, Klaus Aehlig wrote:
On Fri, Jul 10, 2015 at 02:06:32AM +0300, Oleg Ponomarev wrote:
During the sequence of moves while cluster balancing the situation on
cluster may change (e.g. because of adding new instance or because of
instance or node parameters change) and desired moves can become
unprofitable.
Partly prevent this effect by introducing new hbal option
*--avoid-disk-moves=FACTOR* which will admit only profitable enough
disk moves.
Signed-off-by: Oleg Ponomarev <[email protected]>
---
doc/design-migration-speed-hbal.rst | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
create mode 100644 doc/design-migration-speed-hbal.rst
The design looks good, but please format it in the way consistent
with our current practises.
- new files that should be part of the distribution tar ball
(in particular all source files and designs) need to be registered
in Makefile.am
- each design document must be part of some toc-tree; for new designs
(i.e., those not implemented in a stable release) the place to mention
them is doc/design-drafts.rst (just add to the end of the list).
diff --git a/doc/design-migration-speed-hbal.rst
b/doc/design-migration-speed-hbal.rst
new file mode 100644
index 0000000..ff3fd51
--- /dev/null
+++ b/doc/design-migration-speed-hbal.rst
@@ -0,0 +1,28 @@
+========================================
+Migration speed accounting in Hbal
+========================================
over/underlines should have the same length (number of characters as)
the heading
+
+.. contents:: :depth: 2
+
+Hbal usually performs complex sequence of moves during cluster balancing in
+order to achieve local optimal cluster state. Unfortunately, each move may take
+significant amount of time. Thus, during the sequence of moves the situation on
+cluster may change (e.g. because of adding new instance or because of instance
add comma after "e.g."
+or node parameters change) and desired moves can become unprofitable.
+
+Usually disk moves become a bottleneck and require sufficient amount of time.
+:doc:`design-move-instance-improvement` considers disk moves speed in more
References to a design document get rendered as a link with the link text
being the title of that document, in this case "Instance move improvements".
With
this text in the place of the reference, the sentence becomes ungrammatical.
(You can look at existing design documents to see how references are usually
done.)
+details. Currently, Ganeti have a ``--no-disk-moves`` option preventing disk
s/have/has
Also, it is not Ganeti that has this option, but the ``htools``, or, more
specifically ``hbal``.
+moves during cluster balancing in order to perform fast (but of course non
+optimal) balancing. It may be useful but ideally we need to find a balance
add comma before "but"
+between optimal configuration and time to reach this configuration.
+
+Avoiding inssignificnt disk moves
+=================================
s/inssignificnt/insignificant/
+
+Allowing only profitable enough disk moves may become a first step to reach
+a compromise between moves speed and optimal scoring. This can be implemented
+by introducing ``--avoid-disk-moves *FACTOR*`` option which will admit disk
+moves only if the gain in the cluster metrics is :underline: 'FACTOR' times
+higher than the gain achievable by non disk moves.
+
--
1.9.1
--
Sincerely, Oleg Ponomarev <[email protected]>
