Is there solution for viewing chunks distribution in ceph's pools with erasure code?

Question

According to the picture from this page ceph splits objects on chunks and writes them on osds.

For viewing objects distribution with replication algorithm I can use commands like ceph pg dump or ceph osd map. But I can't find commands to view data chunk distribution.

Answer 1

You can use the ceph-objectstore-tool to query offline OSDs and see which OSD contains which data chunk:

[ceph: root@pacific /]# ceph-objectstore-tool --data-path /var/lib/ceph/osd/ceph-1/ --op list 
["11.2s2",{"oid":"file","key":"","snapid":-2,"hash":779072666,"max":0,"pool":11,"namespace":"","shard_id":2,"max":0}]

The first entry contains the shard ID: "11.2s2". So the PG is 11.2 and shard ID is 2. To query a cephadm deployed OSD you need to stop it via cephadm and then enter the container:

pacific:~ # cephadm unit stop --name osd.1
Inferring fsid 0a8034bc-15f4-11ec-8330-fa163eed040c
pacific:~ # cephadm shell --name osd.1