Ceph: Designing and Implementing Scalable Storage Systems

How to do it...

We will now take a look at the CRUSH map of our Ceph cluster:

1. Extract the CRUSH map from any of the monitor nodes:

        # ceph osd getcrushmap -o crushmap_compiled_file

2. Once you have the CRUSH map, decompile it to convert it into a human-readable/editable form:

        # crushtool -d crushmap_compiled_file                     -o crushmap_decompiled_file

At this point, the output file, crushmap_decompiled_file, can be viewed/edited in your favorite editor. In the next recipe, we will learn how to perform changes to the CRUSH map.

3. Once the changes are done, you should compile these changes:

        # crushtool -c crushmap_decompiled_file -o newcrushmap

4. Finally, inject the newly compiled CRUSH map into the Ceph cluster:

 # ceph osd setcrushmap -i newcrushmap ...