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doc: add documentation regarding read affinity

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This commit adds documentation about read affinity supported
for rbd volumes.

Signed-off-by: Rakshith R <rar@redhat.com>
This commit is contained in:
Rakshith R 2023-02-02 17:23:08 +05:30 committed by mergify[bot]
parent 95682522ee
commit db8320ce51
2 changed files with 34 additions and 0 deletions
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9
deploy/rbd/kubernetes/csi-rbdplugin.yaml
View File

@ -68,6 +68,15 @@ spec:
# and pass the label names below, for CSI to consume and advertise
# its equivalent topology domain
# - "--domainlabels=failure-domain/region,failure-domain/zone"
#
# Options to enable read affinity.
# If enabled Ceph CSI will fetch labels from kubernetes node and
# pass `read_from_replica=localize,crush_location=type:value` during
# rbd map command. refer:
# https://docs.ceph.com/en/latest/man/8/rbd/#kernel-rbd-krbd-options
# for more details.
# - "--enable-read-affinity=true"
# - "--crush-location-labels=topology.io/zone,topology.io/rack"
env:
- name: POD_IP
valueFrom:

25
docs/deploy-rbd.md
View File

@ -48,6 +48,8 @@ make image-cephcsi
| `--skipforceflatten` | `false` | skip image flattening on kernel < 5.2 which support mapping of rbd images which has the deep-flatten feature |
| `--maxsnapshotsonimage` | `450` | Maximum number of snapshots allowed on rbd image without flattening |
| `--setmetadata` | `false` | Set metadata on volume |
| `--enable-read-affinity` | `false` | enable read affinity |
| `--crush-location-labels`| _empty_ | Kubernetes node labels that determine the CRUSH location the node belongs to, separated by ',' |
**Available volume parameters:**
@ -196,6 +198,29 @@ The Helm chart is located in `charts/ceph-csi-rbd`.
[See the Helm chart readme for installation instructions.](../charts/ceph-csi-rbd/README.md)
## Read Affinity using crush locations for RBD volumes
Ceph CSI supports mapping RBD volumes with krbd options
`"read_from_replica=localize,crush_location=type1:value1|type2:value2"` to
allow serving reads from the most local OSD (according to OSD locations as
defined in the CRUSH map).
Refer [krbd-options](https://docs.ceph.com/en/latest/man/8/rbd/#kernel-rbd-krbd-options)
for more details.
This can be enabled by adding labels to Kubernetes nodes like
`"topology.io/region=east"` and `"topology.io/zone=east-zone1"` and
passing command line arguments `"--enable-read-affinity=true"` and
`"--crush-location-labels=topology.io/zone,topology.io/region"` to Ceph CSI
RBD daemonset pod "csi-rbdplugin" container, resulting in Ceph CSI adding
`"--options read_from_replica=localize,crush_location=zone:east-zone1|region:east"`
krbd options during rbd map operation.
If enabled, this option will be added to all RBD volumes mapped by Ceph CSI.
Well known labels can be found
[here](https://kubernetes.io/docs/reference/labels-annotations-taints/).
>Note: Label values will have all its dots `"."` normalized with dashes `"-"`
in order for it to work with ceph CRUSH map.
## Encryption for RBD volumes
> Enabling encryption on volumes created without encryption is **not supported**