Create new MGR pool (.mgr) in Proxmox VE

The .mgr pool in Ceph safes meta data for the Ceph manager daemon (ceph-mgr) that are required for the supervision and the management of the cluster. In the event of mistakes within the manager, it is possible to restart the pool. This article is a short instruction for the recreation of the .mgr- pool.

Description of problem

It may occur that there are error messages regarding the .mgr pool within Proxmox Ceph HCI. For example, the following mistake can appear:

pg 1.0 num got status unknown

Recreation of .mgr pools

Hint: The .mgr-pool for Proxmox systems with Ceph 16.X or older is called different: device_health_metrics!

The pool has to be restarted to fix the error. To find out which pool belongs to which placement group, you can execute the following command:

root@pve-b11:~# ceph osd lspools
1 .mgr
5 vm_nvme
6 cephfs_data
7 cephfs_metadata

The Placement Group 1 is also assigned to the .mgr-pool. The .mgr-pool can be recreated without effects.

The procedure is as follows:

1. delete MGR pool under Host / Ceph / Pool
2. delete the active manager service under Host -> Ceph -> Monitor
3. wait until a standby manager service is active, only then the old deleted MGR service entry will disappear
4. recreate the manager service that has just been deleted on the respective host

Now, a new .mgr-pool has been created, which is fully functional.

Author: Jonas Sterr Jonas Sterr has been working for Thomas-Krenn for several years. Originally employed as a trainee in technical support and then in hosting (formerly Filoo), Mr. Sterr now mainly deals with the topics of storage (SDS / Huawei / Netapp), virtualization (VMware, Proxmox, HyperV) and network (switches, firewalls) in product management at Thomas-Krenn.AG in Freyung.

Translator: Alina Ranzinger Alina has been working at Thomas-Krenn.AG since 2024. After her training as multilingual business assistant, she got her job as assistant of the Product Management and is responsible for the translation of texts and for the organisation of the department.