Support volume resize

[jieyu]

There are use cases for both volume size growth and volume size shrinking.

For instance, a database application is using a volume, and later find out that it needs more space. Migrating the data will be very expensive. If the underlying storage provider supports volume resize, the more preferable way is to resize the volume.

Although a volume can be resized by talking to the storage backend directly, it's more appropriate for CO to be aware that operation so that CO can update the relevant information about the volume in CO's state (consistency). Also, for some CO like Mesos, before the resize operation, it also needs to make sure that the storage backend has enough resources (or quota) for the volume resize to be successful. Given above, the CSI spec should have volume resize support.

Some CO issues that are related to this topic:
MESOS-4965
Kubernetes 35941

[gnufied]

Design proposal merged in Kubernetes - https://github.com/kubernetes/community/blob/master/contributors/design-proposals/storage/grow-volume-size.md

I am starting on this for CSI. Should quota check be a part of CSI at all? In Kubernetes - this concern is offloaded to a admission controller and is not really part of standard resizing workflow.

[jdef]

Lets keep it simple for now and avoid the concept of quota in CSI

…

On Wed, Apr 11, 2018 at 9:35 AM, Hemant Kumar ***@***.***> wrote: Design proposal merged in Kubernetes - https://github.com/kubernetes/ community/blob/master/contributors/design-proposals/ storage/grow-volume-size.md I am starting for on this for CSI. Should quota check be a part of CSI at all? In Kubernetes - this concern is offloaded to a admission controller and is not really part of standard resizing workflow. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#212 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ACPVLJIRZh_MD5g7WGhwTfGZmibOk6VEks5tngafgaJpZM4SuI62> .

[gpaul]

For mount volumes we support specifying an fs_type. This field can be trivially used to format the volume with the given fs_type provided the necessary filesystem libraries are installed on the node. For example

mkfs -t ext4 /dev/sda
mkfs -t xfs /dev/sdb

However, there is no such standard utility for resizing filesystems:

resize2fs /dev/sda
xfs_growfs /dev/sdb

This means that CSI plugins that today support arbitrary filesystems will need to be modified to add individual support for each filesystems they intend to support.

[jdef]

#231

[saad-ali]

Spoke with @gnufied. This is not a blocker for 0.3. Moving it out of milestone.

[saad-ali]

PR in progress: #222

[saad-ali]

This is not a blocker for 1.0.rc