[Pkg-ganeti-devel] [ganeti] 38/165: Document the changed allocation heuristics in the man page

[Apollon Oikonomopoulos]

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commit ea6c897fb345f324feb630f96ccafbbdc4a43cdb
Author: Klaus Aehlig <aehlig at google.com>
Date:   Fri Jan 30 17:31:42 2015 +0100

    Document the changed allocation heuristics in the man page
    
    ..stating that for allocations on exclusive-storage node groups
    we use the lost-allocations metrics, and giving its definition.
    
    Signed-off-by: Klaus Aehlig <aehlig at google.com>
    Reviewed-by: Petr Pudlak <pudlak at google.com>
---
 man/hail.rst | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/man/hail.rst b/man/hail.rst
index e11442a..67408db 100644
--- a/man/hail.rst
+++ b/man/hail.rst
@@ -34,7 +34,9 @@ the CPUload collector.
 ALGORITHM
 ~~~~~~~~~
 
-The program uses a simplified version of the hbal algorithm.
+On regular node groups, the program uses a simplified version of
+the hbal algorithm; for allocation on node groups with exclusive
+storage see below.
 
 For single-node allocations (non-mirrored instances), again we
 select the node which, when chosen as the primary node, gives the best
@@ -64,6 +66,17 @@ The deprecated *multi-evacuate* modes is no longer supported.
 In all cases, the cluster (or group) scoring is identical to the hbal
 algorithm.
 
+For allocation on node groups with exclusive storage, the lost-allocations
+metrics is used instead to determine which node to allocate an instance
+on. For a node the allocation vector is the vector of, for each instance
+policy interval in decreasing order, the number of instances minimally
+compliant with that interval that still can be placed on that node. The
+lost-allocations vector for an instance on a node is the difference of
+the allocation vectors for that node before and after placing the
+instance on that node. The lost-allocations metrics is the lost allocation
+vector followed by the remaining disk space on the chosen node, all
+compared lexicographically.
+
 OPTIONS
 -------
 

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