Storage motion for Hyper-V

Bug Reference

CLOUDSTACK-6143

Branch

4.4, master

Introduction

Hyper-V 2012 R2 allows migration of volumes (virtual disks) of a virtual machine from one storage to another, while the virtual machine continues to run. It also allows live migration of a virtual machine and its volumes to another host and storage without any downtime.

The intend of this feature is to enable support of live migration of a virtual machines with its volumes across hosts and storage pools. It'll also migration of volumes across storage pools while the volume stays attached to a running virtual machine.

Purpose

This is a feature specification for supporting storage motion on Hyper-V.

References

• Storage motion in cloudstack
• http://blogs.technet.com/b/canitpro/archive/2013/03/21/step-by-step-completing-storage-live-migration-in-hyper-v.aspx
• http://msdn.microsoft.com/en-us/library/hh850079(v=vs.85).aspx

Document History

Glossary

Instance/vm - Virtual machine running on a hypervisor. The terms may be used interchangeably.

Live migration - Migrating a vm from one host to another without any downtime of the vm,

Volume live migration - Migrating a volume of a vm from one storage pool to another without any downtime of the vm.

Feature Specifications

Scenarios

Storage motion operations can only carried out by a CloudStack root administrator. Summary of the operations that storage motion will allow on Hyper-V

• Scenario 1: Live migrating volume of a virtual machine. Virtual machine stays running on the same host.
  
  • A volume deployed on a local storage cannot be migrated to another storage pool. The volume has been created with a 'Disk Offering' as local. It can only reside on a local storage pool. Since the volume is attached to a running vm and is on a local storage it cannot be live migrated to another local storage pool on another host.

  • A volume on a cluster wide shared storage can be migrated to a another cluster wide shared storage within the same CloudStack cluster.
    
    Following table summarizes the scenario

    	Destination Storage type = Local	Destination Storage type = Shared
    Source Storage type = Local	No	No
    Source Storage type = Shared	No	Yes

• Scenario 2: Live migrating a virtual machine with its volumes to another host and storage pool respectively.
  • A vm with its volumes on a local storage storage can be live migrated to another host which has local storage attached. The volume of the vm will be placed on the local storage on the destination host. The host may be within the cluster or in another cluster.
  • A vm with its volumes on a shared storage can be live migrated to another host which a shared storage pool attached to it. The host may be within the cluster or in another cluster.

  • A vm with volumes on both shared and local storage can be live migrated to another host if the destination host has access to both shared and local storage. Source volumes on shared storage will be migrated to shared storage accessible on the destination. Similarly, volumes on local storage will be migrated to local storage on the destination.
    
    Following table summarizes the scenario

    	Destination Storage type = Local	Destination Storage type = Shared
    Source Storage type = Local	Yes	No
    Source Storage type = Shared	No	Yes

    
    

• Unsupported Scenario: A volume on a local storage cannot be live migrated to a volume of shared storage. A volume on local storage is created by a disk offering of  type "Local". Migrating it to a shared storage will conflict with the disk offering. The same applies to not allowing migration of a volume from shared to local storage.

Test Guidelines

Functional

• For migrating a volume from one storage pool to another, only the shared storage pools within the cluster should be listed.
• Instance with one volume (only Root volume). Migrate volume of an instance from one shared storage pool to another within the cluster. At the end of the operation the volume should be on the destination pool and path updated in the db.
• Instance with multiple volumes (Root and Data volumes). Migrate one volume from one shared storage pool to another. At the end of the operation the volume should be on the destination pool and path updated in the db.
• If storage tags were used in disk offerings, findStoragePoolsForMigration api should return the storage pools with matching tags as suitable. Other shared storage pools in the cluster should be marked unsuitable.

Negative

• specify supportability characteristics:
  • what new logging (or at least the important one) is introduced
  • how to debug and troubleshoot
  • what are the audit events 
  • list JMX interfaces
  • graceful failure and recovery scenarios
  • possible fallback or work around route if feature does not work as expected, if those workarounds do exist ofcourse.
  • if feature depends other run-time environment related requirements, provide sanity check list for support people to run
• explain configuration characteristics:
  • configuration parameters or files introduced/changed
  • branding parameters or files introduced/changed
  • highlight parameters for performance tweaking
  • highlight how installation/upgrade scenarios change
• deployment requirements (fresh install vs. upgrade) if any
• system requirements: memory, CPU, desk space, etc
• interoperability and compatibility requirements:
  • OS
  • xenserver, hypervisors
  • storage, networks, other
• list localization and internationalization specifications 
• explain the impact and possible upgrade/migration solution introduced by the feature 
• explain performance & scalability implications when feature is used from small scale to large scale
• explain levels or types of users communities of this feature (e.g. admin, user, etc)

Use cases

No new apis have been added for this feature. Existing apis; explained in Storage motion in cloudstack; will enable storage motion for Hyper-V too. List of apis used for storage motion

• findStoragePoolsForMigration. For listing the suitable storage pools to which a volume of a vm can be live migrated too.
• migrateVolume. For live migrating a volume of a vm to another storage pool. 'livemigrate' parameter to the api should be true.
• findHostsForMigration. For listing the suitable hosts to which a vm can be live migrated along with its volumes. In the response object; HostForMigrationResponse; 'requiresStorageMotion' attribute/flag is set to 'true' if migrating the vm the host requires storage motion.
• migrateVirtualMachineWithVolume. For live migrating a vm with its volumes to a host.

Since these are existing apis; they are not explained here. Please refer to Storage motion in cloudstack for api details.

Architecture and Design description

• discussion of alternatives amongst design ideas, their resources/time tradeoffs and limitations. Explain why a certain design idea is chosen over others
• highlight architectural patterns being used (queues, async/sync, state machines, etc)
• talk about main algorithms used
• explain what components are being changed and what the dependent components are
• regarding database: talk about tables being added/modified
• performance implications: what are the improvements or risks introduced to capacity, response time, resources usage and other relevant KPIs
• preferably show class diagrams, sequence diagrams and state diagrams
• if possible, publish signatures of all methods classes and interfaces implement, and the explain the object information of different classes

Web Services APIs

list changes to existing web services APIs and new APIs introduced with signatures and throughout documentation

UI flow

• either demonstrate it visually here or link to relevant mockups

IP Clearance

• what dependencies will you be adding to the project?
• are you expecting to include any code developed outside the Apache CloudStack project?

Appendix

Appendix A:

Appendix B: