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man: osdmaptool: document test-map-pgs* options

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Signed-off-by: Kefu Chai <kchai@redhat.com>
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Kefu Chai 2016-05-16 18:57:43 +08:00
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doc/man/8/osdmaptool.rst
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@ -49,6 +49,15 @@ Options
be set with bitsperosd bits per OSD. That is, the pg_num map
attribute will be set to numosd shifted by bitsperosd.
.. option:: --test-map-pgs [--pool poolid]
will print out the mappings from placement groups to OSDs.
.. option:: --test-map-pgs-dump [--pool poolid]
will print out the summary of all placement groups and the mappings
from them to the mapped OSDs.
Example
=======
@ -61,6 +70,77 @@ To view the result::
osdmaptool --print osdmap
To view the mappings of placement groups for pool 0::
osdmaptool --test-map-pgs-dump rbd --pool 0
pool 0 pg_num 8
0.0 [0,2,1] 0
0.1 [2,0,1] 2
0.2 [0,1,2] 0
0.3 [2,0,1] 2
0.4 [0,2,1] 0
0.5 [0,2,1] 0
0.6 [0,1,2] 0
0.7 [1,0,2] 1
#osd count first primary c wt wt
osd.0 8 5 5 1 1
osd.1 8 1 1 1 1
osd.2 8 2 2 1 1
in 3
avg 8 stddev 0 (0x) (expected 2.3094 0.288675x))
min osd.0 8
max osd.0 8
size 0 0
size 1 0
size 2 0
size 3 8
In which,
#. pool 0 has 8 placement groups. And two tables follow:
#. A table for placement groups. Each row presents a placement group. With columns of:
* placement group id,
* acting set, and
* primary OSD.
#. A table for all OSDs. Each row presents an OSD. With columns of:
* count of placement groups being mapped to this OSD,
* count of placement groups where this OSD is the first one in their acting sets,
* count of placement groups where this OSD is the primary of them,
* the CRUSH weight of this OSD, and
* the weight of this OSD.
#. Looking at the number of placement groups held by 3 OSDs. We have
* avarge, stddev, stddev/average, expected stddev, expected stddev / average
* min and max
#. The number of placement groups mapping to n OSDs. In this case, all 8 placement
groups are mapping to 3 different OSDs.
In a less-balanced cluster, we could have following output for the statistics of
placement group distribution, whose standard deviation is 1.41421::
#osd count first primary c wt wt
osd.0 8 5 5 1 1
osd.1 8 1 1 1 1
osd.2 8 2 2 1 1
#osd count first primary c wt wt
osd.0 33 9 9 0.0145874 1
osd.1 34 14 14 0.0145874 1
osd.2 31 7 7 0.0145874 1
osd.3 31 13 13 0.0145874 1
osd.4 30 14 14 0.0145874 1
osd.5 33 7 7 0.0145874 1
in 6
avg 32 stddev 1.41421 (0.0441942x) (expected 5.16398 0.161374x))
min osd.4 30
max osd.1 34
size 00
size 10
size 20
size 364
Availability
============