openstack
/
charm-deployment-guide
Code Issues Proposed changes

Add warning about Ceph RBD journal overhead 

Enabling RBD mirroring makes use of the journal feature of RBD's.

This has some significant overheads for write performance so
make sure this is apparent in the documentation for this feature.

Change-Id: I0e10d641606e25f6711d07eed75ba23214ec9bd7
This commit is contained in:
James Page 2019-09-25 13:47:43 +01:00
parent a7073b973d
commit 065b0ec70f
1 changed files with 11 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
deploy-guide/source/app-ceph-rbd-mirror.rst
View File

@ -17,14 +17,19 @@ includes in-depth information on this charm as well as how to use it for
cluster failover and disaster recovery. It also includes more brief deployment
steps as the ones shown here.
.. warning::
RBD mirroring is only one specific element in datacentre redundancy. Refer
to `Ceph RADOS Gateway Multisite Replication`_ and other work to arrive at
a complete solution.
RBD mirroring is only one specific element in datacentre redundancy. Refer
to `Ceph RADOS Gateway Multisite Replication`_ and other work to arrive at
a complete solution.
See `Upstream Ceph documentation on RBD mirroring`_ for complete information.
.. warning::
RBD mirroring makes use of the journalling feature of Ceph; this incurs
an overhead on all write activity on a RBD which will impact performance.
See Florian Haas' excellent performance analysis of `RBD mirror`_ from
Cephalocon Barcelona 2019.
Deployment
++++++++++
@ -208,3 +213,4 @@ You're done.
.. _ceph-rbd-mirror charm project page: https://opendev.org/openstack/charm-ceph-rbd-mirror/src/branch/master/src/README.md
.. _Ceph RADOS Gateway Multisite replication: https://docs.openstack.org/project-deploy-guide/charm-deployment-guide/latest/app-rgw-multisite.html
.. _Upstream Ceph documentation on RBD mirroring: https://docs.ceph.com/docs/mimic/rbd/rbd-mirroring/
.. _RBD mirror: https://fghaas.github.io/cephalocon2019-rbdmirror/#/7/6