Virtualized block device backing for virtualization containers
Technologies are provided for backing virtualization containers with layered storage volumes stored in remote storage devices. A virtualization container can present a virtual storage volume to a process running in the virtualization container and handle data access requests from the process using a layered storage volume based on one or more read-only snapshots stored in one or more remote storage devices. Changes can be recorded in a read-write layer in one or more of the remote storage devices and associated with the layered storage volume. A new read-only snapshot can be created based on the data in the read-write storage layer and associated with the one or more read-only snapshots on which the layered storage volume is based. A virtualization container can be associated with a new layered storage volume based on the created read-only snapshot and the one or more read-only snapshots on which it is based.
1. A method, comprising:
instantiating a virtualization container from a virtualization container image on top of an operating system kernel of a host, wherein the virtualization container image comprises a plurality of read-only image layers;
receiving a command to create a storage volume for the virtualization container based on an image manifest comprising a list of the plurality of read-only image layers of the virtualization container image;
identifying a read-only image layer of the plurality of read-only image layers of the virtualization container image;
searching a remote storage device for a snapshot associated with the read-only image layer of the plurality of read-only image layers of the virtualization container image; and
if a snapshot associated with the read-only image layer of the plurality of read-only image layers of the virtualization container image is found, creating a remote storage volume in the remote storage device based on the snapshot and connecting the virtualization container to the remote storage volume;
otherwise, creating a new snapshot in the remote storage device using data for the read-only image layer of the plurality of read-only image layers of the virtualization container image and connecting the virtualization container to a remote storage volume in the remote storage device that is based on the new snapshot.
2. The method of claim 1 , further comprising:
presenting the new remote storage volume to a process running in the new virtualization container as a mounted volume; and
tunneling data access operations targeting the mounted volume to the remote storage volume.
3. The method of claim 1 , wherein creating the new snapshot in the remote storage device using data for the read-only image layer of the plurality of read-only image layers of the virtualization container image and connecting the virtualization container to a remote storage volume in the remote storage device that is based on the new snapshot comprises:
creating the remote storage volume in the remote storage device;
writing the data for the read-only image layer of the plurality of read-only image layers of the virtualization container image to a read-write storage layer of the remote storage volume;
creating the new snapshot using the data in the read-write storage layer of the remote storage volume; and
associating the new snapshot with the remote storage volume.
4. The method of claim 1 , further comprising:
receiving a command to create a new image for the virtualization container;
responsive to receiving the command, creating a new snapshot of the remote storage volume connected to the virtualization container, wherein creating the new snapshot of the remote storage volume comprises:
determining differences between the remote storage volume and another snapshot, wherein the another snapshot is a snapshot on which the remote storage volume is based,
storing the differences in the new snapshot, and
associating the new snapshot with the another snapshot with a relationship that indicates the new snapshot is based on the another snapshot;
storing the created snapshot in the remote storage device; and
registering the created snapshot as the new image with an image repository.
5. The method of claim 4 , further comprising:
receiving a data write request from a process running in the virtualization container;
creating a read-write storage layer in the remote storage volume;
writing data contained in the data write request to the read-write storage layer; and
wherein determining differences between the remote storage volume and the another snapshot comprises:
identifying the data written to the read-write storage layer, and
storing a read-only copy of the identified data in the new snapshot.
6. The method of claim 5 , further comprising:
determining that the data write request comprises a request to modify data stored in the another snapshot;
copying the data to be modified from the another snapshot to the read-write storage layer; and
modifying the copy of the data in the read-write storage layer.
7. The method of claim 4 , further comprising:
generating an image manifest that identifies the new snapshot, the another snapshot, and the relationship between the new snapshot and the another snapshot; and
transmitting the image manifest to the image repository.
8. The method of claim 4 , wherein:
the remote storage device is one of multiple storage devices in a distributed block storage; and
storing the new snapshot in the remote storage device comprises storing multiple data blocks associated with the new snapshot in the remote storage device.
9. The method of claim 8 , further comprising:
receiving a request for data from a process running in the virtualization container;
determining that the requested data comprises a data block associated with the new snapshot that is stored in the remote storage device; and
retrieving the data block from the remote storage device.