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add class sections

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This commit is contained in:
Matthew Wong
2016-08-22 23:34:32 -04:00
parent d70418625e
commit 676a4f1577
1 changed files with 50 additions and 48 deletions
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docs/user-guide/persistent-volumes/index.md
+50 -48
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@@ -93,6 +93,8 @@ Each PV contains a spec and status, which is the specification and status of the
kind: PersistentVolume kind: PersistentVolume
metadata: metadata:
name: pv0003 name: pv0003
annotations:
volume.beta.kubernetes.io/storage-class: "slow"
spec: spec:
capacity: capacity:
storage: 5Gi storage: 5Gi
@@ -145,6 +147,16 @@ In the CLI, the access modes are abbreviated to:
| RDB | x | x | - | | RDB | x | x | - |
| VsphereVolume | x | - | - | | VsphereVolume | x | - | - |
### Class
A PV can have a class, which is specified by setting the
"volume.beta.kubernetes.io/storage-class" annotation to the name of a
`StorageClass`. A PV of a particular class can only be bound to PVCs requesting
that class. A PV with no annotation or its class annotation set to `""` has no
class and can only be bound to PVCs that request no particular class.
In the future after beta, the `volume.beta.kubernetes.io/storage-class`
annotation will become an attribute.
### Recycling Policy ### Recycling Policy
@@ -176,6 +188,8 @@ kind: PersistentVolumeClaim
apiVersion: v1 apiVersion: v1
metadata: metadata:
name: myclaim name: myclaim
annotations:
volume.beta.kubernetes.io/storage-class: "slow"
spec: spec:
accessModes: accessModes:
- ReadWriteOnce - ReadWriteOnce
@@ -206,6 +220,36 @@ Claims can specify a [label selector](/docs/user-guide/labels/#label-selectors)
All of the requirements, from both `matchLabels` and `matchExpressions` are ANDed together – they must all be satisfied in order to match. All of the requirements, from both `matchLabels` and `matchExpressions` are ANDed together – they must all be satisfied in order to match.
### Class
A claim can request a particular class by specifying the name of a
`StorageClass`using the annotation `volume.beta.kubernetes.io/storage-class`.
Only PVs of the requested class, ones with the same annotation as the PVC, can
be bound to the PVC.
PVCs don't necessarily have to request a class, they can omit the annotation or
set it to `""`. The cluster treats PVCs that don't request a class differently
depending on whether the
[`SimpleDefaultStorageClassForPVC` admission controller](docs/admin/admission-controllers/#simpledefaultstorageclassforpvc)
is turned on.
* If the admission controller is turned on, the administrator may specify a
default `StorageClass`. All PVCs that don't request a `StorageClass` can be
bound only to PVs of that default. This means that the PVs those PVCs would
normally be bound to, the PVs that have no class (no annotation or annotation
equal to `""`), cannot be bound to any PVC. Specifying a default `StorageClass`
is done by setting the annotation
`storageclass.beta.kubernetes.io/is-default-class` equal to "true" in a
`StorageClass` object. If the administrator does not specify a default, the
cluster will respond to PVC creation as if the admission controller were turned
off. If more than one default is specified, the admission controller will forbid
the creation of all PVCs.
* If the admission controller is turned off, the claim may be bound to volumes
that have no class
In the future after beta, the `volume.beta.kubernetes.io/storage-class`
annotation will become an attribute.
## Claims As Volumes ## Claims As Volumes
Pods access storage by using the claim as a volume. Claims must exist in the same namespace as the pod using the claim. The cluster finds the claim in the pod's namespace and uses it to get the `PersistentVolume` backing the claim. The volume is then mounted to the host and into the pod. Pods access storage by using the claim as a volume. Claims must exist in the same namespace as the pod using the claim. The cluster finds the claim in the pod's namespace and uses it to get the `PersistentVolume` backing the claim. The volume is then mounted to the host and into the pod.
@@ -244,21 +288,10 @@ of a class, all of which are opaque to users, when first creating
`StorageClass` objects, and the objects cannot be updated once they are `StorageClass` objects, and the objects cannot be updated once they are
created. created.
Users don't necessarily have to request a `StorageClass` in their PVC. The Administrators can specify a default `StorageClass` just for PVCs that don't
cluster treats PVCs that don't request a `StorageClass` differently depending request any particular class to bind to: see the
on whether the [`PersistentVolumeClaim` section](docs/user-guide/persistent-volumes/index/#class-1)
[`SimpleDefaultStorageClassForPVC` admission controller](docs/admin/admission-controllers/#simpledefaultstorageclassforpvc) is turned on. for details.
* If the admission controller is turned on, the administrator may specify a
default `StorageClass`. All PVCs that don't request a `StorageClass` will be
bound only to PVs of that default. Specifying a default `StorageClass` is done
by setting the annotation `storageclass.beta.kubernetes.io/is-default-class`
equal to "true" in a `StorageClass` object. If the administrator does not
specify a default, the cluster will respond to PVC creation as if the admission
controller were turned off. If more than one default is specified, the
admission controller will forbid the creation of all PVCs.
* If the admission controller is turned off, the claim may be bound to any
volume that does not belong to a `StorageClass` or that has a blank `""` value
for its `volume.beta.kubernetes.io/storage-class` annotation.
```yaml ```yaml
kind: StorageClass kind: StorageClass
@@ -297,8 +330,8 @@ parameters:
``` ```
* `type`: `io1`, `gp2`, `sc1`, `st1`. See AWS docs for details. Default: `gp2`. * `type`: `io1`, `gp2`, `sc1`, `st1`. See AWS docs for details. Default: `gp2`.
* `zone`: AWS zone. If not specified, a random zone in the same region as * `zone`: AWS zone. If not specified, a random zone where the cluster has a node
controller-manager will be chosen. is chosen
* `iopsPerGB`: only for `io1` volumes. I/O operations per second per GiB. AWS * `iopsPerGB`: only for `io1` volumes. I/O operations per second per GiB. AWS
volume plugin multiplies this with size of requested volume to compute IOPS of volume plugin multiplies this with size of requested volume to compute IOPS of
the volume and caps it at 20 000 IOPS (maximum supported by AWS, see AWS docs). the volume and caps it at 20 000 IOPS (maximum supported by AWS, see AWS docs).
@@ -319,34 +352,3 @@ provisionerParameters:
* `type`: `pd-standard` or `pd-ssd`. Default: `pd-ssd` * `type`: `pd-standard` or `pd-ssd`. Default: `pd-ssd`
* `zone`: GCE zone. If not specified, a random zone in the same region as * `zone`: GCE zone. If not specified, a random zone in the same region as
controller-manager will be chosen. controller-manager will be chosen.
## Requesting a StorageClass
Users request a particular `StorageClass`, i.e. a `PersistentVolume` that
belongs to and has the characteristics described by the `StorageClass`, by
specifying the name of the class in their `PersistentVolumeClaim` using the
annotation `volume.beta.kubernetes.io/storage-class`. Only a PV of the
requested class, one with the same annotation as the PVC, can then be bound to
the PVC.
```yaml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: myclaim
annotations:
"volume.beta.kubernetes.io/storage-class": "slow"
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 10Gi
```
If a PV of the requested class is not found, a new one will be provisioned
using the `StorageClass`.
When a PVC specifies a `LabelSelector` in addition to requesting a
`StorageClass`, the requirements are ANDed together: only a PV of the requested
class and with the requested labels may be bound to the PVC.