Jump to: navigation, search

Xenapi-sm-volume-driver

Revision as of 19:31, 10 March 2011 by Armando (talk)
  • Launchpad Entry: NovaSpec:xenapi-sm-support
  • Created: 1 February 2011
  • Contributors: Armando Migliaccio

Summary

Design and implement a new driver for Nova-Volume, based on XenAPI Storage Manager. This will provide basic storage functionality (like volume creation, and destruction) on a number of different storage back-ends, but it will enable the capability of using more sophisticated storage back-ends for operations like cloning/snapshotting etc. To have an idea of the benefits of using XenAPI SM to provide back-end storage services, the list below shows some of the storage plugins already supported in XenServer/XCP:

  • NFS VHD: SR plugin which stores disks as VHD files on a remote NFS filesystem
  • Local VHD on LVM: SR plugin which represents disks as VHD disks on Logical Volumes within a locally-attached Volume Group
  • HBA LUN-per-VDI driver: SR plugin which represents LUNs as VDIs sourced by hardware HBA adapters, e.g. hardware-based iSCSI or FC support
  • NetApp: SR driver for mapping of LUNs to VDIs on a NETAPP server, providing use of fast snapshot and clone features on the filer
  • LVHD over FC: SR plugin which represents disks as VHDs on Logical Volumes within a Volume Group created on an HBA LUN, e.g. hardware-based iSCSI or FC support
  • iSCSI: Base ISCSI SR driver, provides a LUN-per-VDI. Does not support creation of VDIs but accesses existing LUNs on a target.
  • LVHD over iSCSI: SR plugin which represents disks as Logical Volumes within a Volume Group created on an iSCSI LUN
  • EqualLogic: SR driver for mapping of LUNs to VDIs on a EQUALLOGIC array group, providing use of fast snapshot and clone features on the array

Release Note

No direct impact on user consuming the external HTTP API services. This blueprint enables the use of several storage back-ends by writing a single nova-volume driver, rather than several ones, as many as the specific storage back-ends required to be supported are needed. In due course, leveraging capabilities of specific back-ends, will enable operations like volume snapshotting, cloning, etc. that can be exposed via official API.

Rationale

This new driver will sit alongside drivers already developed like AoE, iSCSI and SAN (both running on commodity boxes running Linux). However, the latter is slightly different as it will still run on commodity hardware, but it access remote controllers on SAN hardware by some protocol like SSH, CLI or custom API. This is clearly undesirable because every time there is a need to support new hardware, a new driver must be designed and developed. The adoption of XenAPI SM will unleash a number of storage back-end that are abstracted with a common API. Moreover, this becomes premium value for service provider clouds or may become differentiator for enterprise private clouds.

User stories

TBD

Assumptions

For the design and implementation of the new Nova-Volume driver, XenAPI for XenServer/XCP is going to be used.

Design

The steps involved in order to support this activity are:

  • Define a number of flags that are going to be used to customize the driver
  • Develop a XenAPISMVolumeDriver class that derives from VolumeDriver

Implementation

UI Changes

There should be no visible changes to the end users, all this work will be behind the API servers.

Code Changes

Most of the changes will be on top of the current code, however there is a possibility where some changes to Nova-Volume Manager are required to make it more general and accommodate the use of XenAPI SM. More when the actual implementation starts.

Migration

This new driver may require changes to the database schema, more to follow once the actual implementation starts. However procedures to migrate DB schema will be provided.

Test/Demo Plan

Unit tests will be provided as code is developed.

Unresolved issues

None at the time of writing

BoF agenda and discussion

None at the time of writing