From b852fa02bd94eba442343f65e17860faca84909d Mon Sep 17 00:00:00 2001 From: Samuel Walladge Date: Tue, 17 Oct 2023 08:29:49 +1030 Subject: [PATCH] Document rationale for erasure coded pools This addresses the questions: - Why doesn't the charm let me use an erasure coded pool as the default? - How do I use the secondary erasure coded pool once it is configured? Change-Id: Ia885ce41043a4cb04a6d92993474c44e9b994c55 --- src/README.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/src/README.md b/src/README.md index 6acd431..5c94b7e 100644 --- a/src/README.md +++ b/src/README.md @@ -71,6 +71,14 @@ created: a replicated pool (for storing MDS metadata) and an erasure coded pool `ceph-osd-replication-count` configuration option only applies to the metadata (replicated) pool. +Note that the replicated pool will be the default pool for all data. +The user must manually configure the secondary erasure coded pool for use, +for example by using [file layouts][file-layouts]. + +It's not recommended to use an erasure coded data pool as the default data pool; +see [createfs docs][createfs] for more explanation. +Thus, the charm does not support this case. + Erasure coded pools can be configured via options whose names begin with the `ec-` prefix. @@ -135,3 +143,5 @@ For general charm questions refer to the OpenStack [Charm Guide][cg]. [cloud-archive-ceph]: https://wiki.ubuntu.com/OpenStack/CloudArchive#Ceph_and_the_UCA [cdg-ceph-erasure-coding]: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-erasure-coding.html [ceph-bluestore-compression]: https://docs.ceph.com/en/latest/rados/configuration/bluestore-config-ref/#inline-compression +[createfs]: https://docs.ceph.com/en/latest/cephfs/createfs/ +[file-layouts]: https://docs.ceph.com/en/latest/cephfs/file-layouts/