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Update docs with topology aware dynamic provisioning (#9939)

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* Document topology aware volume binding feature

* update for readability

* Update storage-classes.md

* comma splice

* don't abbreviate
This commit is contained in:
Michelle Au
2018-09-11 10:55:30 -07:00
committed by k8s-ci-robot
parent 462817a674
commit e1e655507d
3 changed files with 99 additions and 17 deletions
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content/en/docs/concepts/storage/dynamic-provisioning.md
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@@ -124,6 +124,13 @@ Note that there can be at most one *default* storage class on a cluster, or
a `PersistentVolumeClaim` without `storageClassName` explicitly specified cannot
be created.
## Topology Awareness
In [Multi-Zone](/docs/setup/multiple-zones) clusters, Pods can be spread across
Zones in a Region. Single-Zone storage backends should be provisioned in the Zones where
Pods are scheduled. This can be accomplished by setting the [Volume Binding
Mode](/docs/concepts/storage/storage-classes/#volume-binding-mode).
{{% /capture %}}
content/en/docs/concepts/storage/storage-classes.md
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@@ -55,6 +55,7 @@ parameters:
reclaimPolicy: Retain
mountOptions:
- debug
volumeBindingMode: Immediate
```
### Provisioner
@@ -64,7 +65,7 @@ for provisioning PVs. This field must be specified.
| Volume Plugin | Internal Provisioner| Config Example |
| :--- | :---: | :---: |
| AWSElasticBlockStore | ✓ | [AWS](#aws) |
| AWSElasticBlockStore | ✓ | [AWS EBS](#aws-ebs) |
| AzureFile | ✓ | [Azure File](#azure-file) |
| AzureDisk | ✓ | [Azure Disk](#azure-disk) |
| CephFS | - | - |
@@ -72,7 +73,7 @@ for provisioning PVs. This field must be specified.
| FC | - | - |
| Flexvolume | - | - |
| Flocker | ✓ | - |
| GCEPersistentDisk | ✓ | [GCE](#gce) |
| GCEPersistentDisk | ✓ | [GCE PD](#gce-pd) |
| Glusterfs | ✓ | [Glusterfs](#glusterfs) |
| iSCSI | - | - |
| Quobyte | ✓ | [Quobyte](#quobyte) |
@@ -118,6 +119,74 @@ If the volume plugin does not support mount options but mount options are
specified, provisioning will fail. Mount options are not validated on either
the class or PV, so mount of the PV will simply fail if one is invalid.
### Volume Binding Mode
{{< feature-state for_k8s_version="v1.12" state="beta" >}}
**Note:** This feature requires the `VolumeScheduling` feature gate to be
enabled.
The `volumeBindingMode` field controls when [volume binding and dynamic
provisioning](/docs/concepts/storage/persistent-volumes/#provisioning) should occur.
By default, the `Immediate` mode indicates that volume binding and dynamic
provisioning occurs once the PersistentVolumeClaim is created. For storage
backends that are topology-constrained and not globally accessible from all Nodes
in the cluster, PersistentVolumes will be bound or provisioned without knowledge of the Pod's scheduling
requirements. This may result in unschedulable Pods.
A cluster administrator can address this issue by specifying the `WaitForFirstConsumer` mode which
will delay the binding and provisioning of a PersistentVolume until a Pod using the PersistentVolumeClaim is created.
PersistentVolumes will be selected or provisioned conforming to the topology that is
specified by the Pod's scheduling constraints. These include, but are not limited to, [resource
requirements](/docs/concepts/configuration/manage-compute-resources-container),
[node selectors](/docs/concepts/configuration/assign-pod-node/#nodeselector),
[pod affinity and
anti-affinity](/docs/concepts/configuration/assign-pod-node/#affinity-and-anti-affinity),
and [taints and tolerations](/docs/concepts/configuration/taint-and-toleration).
The following plugins support `WaitForFirstConsumer` with dynamic provisioning:
* [AWSElasticBlockStore](#aws-ebs)
* [GCEPersistentDisk](#gce-pd)
* [AzureDisk](#azure-disk)
The following plugins support `WaitForFirstConsumer` with pre-created PersistentVolume binding:
* All of the above
* [Local](#local)
### Allowed Topologies
{{< feature-state for_k8s_version="v1.12" state="beta" >}}
**Note:** This feature requires the `VolumeScheduling` feature gate to be
enabled.
When a cluster operactor specifies the `WaitForFirstConsumer` volume binding mode, it is no longer necessary
to restrict provisioning to specific topologies in most situations. However,
if still required, `allowedTopologies` can be specified.
This example demonstrates how to restrict the topology of provisioned volumes to specific
zones and should be used as a replacement for the `zone` and `zones` parameters for the
supported plugins.
```yaml
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: standard
provisioner: kubernetes.io/gce-pd
parameters:
type: pd-standard
volumeBindingMode: WaitForFirstConsumer
allowedTopologies:
- matchLabelExpressions:
- key: failure-domain.beta.kubernetes.io/zone
values:
- us-central1-a
- us-central1-b
```
## Parameters
Storage classes have parameters that describe volumes belonging to the storage
@@ -126,7 +195,7 @@ class. Different parameters may be accepted depending on the `provisioner`. For
`iopsPerGB` are specific to EBS. When a parameter is omitted, some default is
used.
### AWS
### AWS EBS
```yaml
kind: StorageClass
@@ -136,7 +205,6 @@ metadata:
provisioner: kubernetes.io/aws-ebs
parameters:
type: io1
zones: us-east-1d, us-east-1c
iopsPerGB: "10"
fsType: ext4
```
@@ -144,10 +212,10 @@ parameters:
* `type`: `io1`, `gp2`, `sc1`, `st1`. See
[AWS docs](http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/EBSVolumeTypes.html)
for details. Default: `gp2`.
* `zone`: AWS zone. If neither `zone` nor `zones` is specified, volumes are
* `zone` (Deprecated): AWS zone. If neither `zone` nor `zones` is specified, volumes are
generally round-robin-ed across all active zones where Kubernetes cluster
has a node. `zone` and `zones` parameters must not be used at the same time.
* `zones`: A comma separated list of AWS zone(s). If neither `zone` nor `zones`
* `zones` (Deprecated): A comma separated list of AWS zone(s). If neither `zone` nor `zones`
is specified, volumes are generally round-robin-ed across all active zones
where Kubernetes cluster has a node. `zone` and `zones` parameters must not
be used at the same time.
@@ -164,7 +232,10 @@ parameters:
encrypting the volume. If none is supplied but `encrypted` is true, a key is
generated by AWS. See AWS docs for valid ARN value.
### GCE
**Note:** `zone` and `zones` parameters are deprecated and replaced with
[allowedTopologies](#allowed-topologies)
### GCE PD
```yaml
kind: StorageClass
@@ -174,15 +245,14 @@ metadata:
provisioner: kubernetes.io/gce-pd
parameters:
type: pd-standard
zones: us-central1-a, us-central1-b
replication-type: none
```
* `type`: `pd-standard` or `pd-ssd`. Default: `pd-standard`
* `zone`: GCE zone. If neither `zone` nor `zones` is specified, volumes are
* `zone` (Deprecated): GCE zone. If neither `zone` nor `zones` is specified, volumes are
generally round-robin-ed across all active zones where Kubernetes cluster has
a node. `zone` and `zones` parameters must not be used at the same time.
* `zones`: A comma separated list of GCE zone(s). If neither `zone` nor `zones`
* `zones` (Deprecated): A comma separated list of GCE zone(s). If neither `zone` nor `zones`
is specified, volumes are generally round-robin-ed across all active zones
where Kubernetes cluster has a node. `zone` and `zones` parameters must not
be used at the same time.
@@ -199,6 +269,9 @@ specified, Kubernetes will arbitrarily choose among the specified zones. If the
`zones` parameter is omitted, Kubernetes will arbitrarily choose among zones
managed by the cluster.
**Note:** `zone` and `zones` parameters are deprecated and replaced with
[allowedTopologies](#allowed-topologies)
### Glusterfs
```yaml
content/en/docs/setup/multiple-zones.md
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@@ -73,18 +73,20 @@ available and can tolerate the loss of a zone, the control plane is
located in a single zone. Users that want a highly available control
plane should follow the [high availability](/docs/admin/high-availability) instructions.
### Volume limitations
The following limitations are addressed with [topology-aware volume binding](/docs/concepts/storage/storage-classes/#volume-binding-mode).
* StatefulSet volume zone spreading when using dynamic provisioning is currently not compatible with
pod affinity or anti-affinity policies.
pod affinity or anti-affinity policies.
* If the name of the StatefulSet contains dashes ("-"), volume zone spreading
may not provide a uniform distribution of storage across zones.
may not provide a uniform distribution of storage across zones.
* When specifying multiple PVCs in a Deployment or Pod spec, the StorageClass
needs to be configured for a specific, single zone, or the PVs need to be
statically provisioned in a specific zone. Another workaround is to use a
StatefulSet, which will ensure that all the volumes for a replica are
provisioned in the same zone.
needs to be configured for a specific single zone, or the PVs need to be
statically provisioned in a specific zone. Another workaround is to use a
StatefulSet, which will ensure that all the volumes for a replica are
provisioned in the same zone.
## Walkthrough