Adjusting existing Erasure Code profiles due to CRUSHMAP changes.

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Environment

SUSE Enterprise Storage 5.x
SUSE Enterprise Storage 6

Situation

The crushmap was modified and the failure domains or crush-root entries of existing Erasure Code (EC) profiles now point to renamed or removed non existing crushmap entries.

Resolution

The failure domain or crush-root for an existing EC profile can be adjusted using the following example command:

ceph osd erasure-code-profile set <profile-name> <parameter>=<value> --force

e.g.

ceph osd erasure-code-profile set default crush-device-class=<enter_existing_value> crush-failure-domain=<enter_existing_value> crush-root=datacenter k=<enter_existing_value> m=<enter_existing_value> --force

IMPORTANT: See the Additional Information section since not all parameters are supported to be changed. When changing any one of the <crush-*> parameters, the other existing parameters listed above need to be specified with their current values, including the existing k= and m= values.

Cause

CRUSHMAP entries were renamed or removed.

Additional Information

In most cases this will be relevant when a CRUSHMAP was previously using separate crush root hierarchies to distinguish between spinning (HDD) and solid state (SSD) devices. This was done since there was no OSD device class crush property yet with earlier Ceph versions.

In such a case, updating to a Ceph version that does support device classes, the crushmap can be updated to use the OSD device class instead. Any existing EC profiles however will for example still point to the now non existent crush-root's, hence requiring an update.

Note that 'crush-*' parameters in profiles are used only at the moment of rule creation and will not update / have any effect on already existing rules that were created previously using a specific profile.

NOTE: Other values, like the k/m values, are however still relevant for existing Pools that were created using an existing profile and therefor can and should not be changed. Modifying the EC plugin or K/M values of an existing profile is therefor NOT allowed or supported. It is recommended to instead create a new profile when creating a new pool that requires different K/M and plugin values.

Disclaimer

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