--compile|-c map.txt

will compile a plaintext map.txt into a binary map file.

--decompile|-d map

will take the compiled map and decompile it into a plaintext source file, suitable for editing.

--build --num_osds {num-osds} layer1 ...

will create map with the given layer structure. See below for a detailed explanation.

--test

will perform a dry run of a CRUSH mapping for a range of input values [--min-x,--max-x] (default [0,1023]) which can be thought of as simulated Placement Groups. See below for a more detailed explanation.

--show-statistics

Displays a summary of the distribution. For instance:

rule 1 (metadata) num_rep 5 result size == 5:    1024/1024

shows that rule 1 which is named metadata successfully mapped 1024 values to result size == 5 devices when trying to map them to num_rep 5 replicas. When it fails to provide the required mapping, presumably because the number of tries must be increased, a breakdown of the failures is displayed. For instance:

rule 1 (metadata) num_rep 10 result size == 8:   4/1024
rule 1 (metadata) num_rep 10 result size == 9:   93/1024
rule 1 (metadata) num_rep 10 result size == 10:  927/1024

shows that although num_rep 10 replicas were required, 4 out of 1024 values ( 4/1024 ) were mapped to result size == 8 devices only.

--show-mappings

Displays the mapping of each value in the range [--min-x,--max-x]. For instance:

CRUSH rule 1 x 24 [11,6]

shows that value 24 is mapped to devices [11,6] by rule 1.

--show-bad-mappings

Displays which value failed to be mapped to the required number of devices. For instance:

bad mapping rule 1 x 781 num_rep 7 result [8,10,2,11,6,9]

shows that when rule 1 was required to map 7 devices, it could map only six : [8,10,2,11,6,9].

--show-utilization

Displays the expected and actual utilization for each device, for each number of replicas. For instance:

device 0: stored : 951      expected : 853.333
device 1: stored : 963      expected : 853.333
...

shows that device 0 stored 951 values and was expected to store 853. Implies --show-statistics.

--show-utilization-all

Displays the same as --show-utilization but does not suppress output when the weight of a device is zero. Implies --show-statistics.

--show-choose-tries

Displays how many attempts were needed to find a device mapping. For instance:

0:     95224
1:      3745
2:      2225
..

shows that 95224 mappings succeeded without retries, 3745 mappings succeeded with one attempts, etc. There are as many rows as the value of the --set-choose-total-tries option.

--output-csv

Creates CSV files (in the current directory) containing information documented by --help-output. The files are named after the rule used when collecting the statistics. For instance, if the rule : 'metadata' is used, the CSV files will be:

metadata-absolute_weights.csv
metadata-device_utilization.csv
...

The first line of the file shortly explains the column layout. For instance:

metadata-absolute_weights.csv
Device ID, Absolute Weight
0,1
...

--output-name NAME

Prepend NAME to the file names generated when --output-csv is specified. For instance --output-name FOO will create files:

FOO-metadata-absolute_weights.csv
FOO-metadata-device_utilization.csv
...