Knowledge Base
vMotion over Distance support with EMC VPLEX Metro
Purpose
This article provides information about the support of vMotion over Distance operations over VPLEX Metro using Distributed Virtual Volume. It also specifies the VMware ESX host and VPLEX configuration details and expected behavior under different operational scenarios.
Resolution
About EMC VPLEX
EMC VPLEX is a new federation solution that can be stretched across 2 geographically dispersed datacenters separated by synchronous distances (maximum distance of separation=100km, maximum round trip latency=5 ms RTT). It provides simultaneous access to storage devices at 2 sites through creation of VPLEX Distributed Virtual Volume. For more information about Distributed Virtual Volume, see Additional Information in this article.
Provided all vMotion over Distance requirements are met, with Distributed Virtual volume configured on VPLEX, a distant VMotion operation can be done from Datacenter 1 and Datacenter 2. You can vMotion over Distance a virtual machine from one datacenter to another to avoid disasters, migrate workloads to save power, or load balance workloads.
Notes:
- See Requirements in this article for more information about the requirements for vMotion over Distance.
- See Best practice documents in this article for more information about Distributed Virtual Volume on VPLEX.
This graphic demonstrates vMotion over Distance over VPLEX Distributed volume:
Requirements
To perform a vMotion over Distance operation successfully over synchronous distance, the following requirements must be met:
- An IP network with a minimum bandwidth of 622 Mbps is required.
- The maximum latency between the two VMware vSphere servers cannot exceed 5 milliseconds (ms).
- The source and destination ESX servers must have a private network on the same IP subnet and broadcast domain.
- The IP subnet on which the virtual machine resides must be accessible from both the source and destination ESX servers. This requirement is very important because a virtual machine retains its IP address when it moves to the destination ESX server to help ensure that its communication with the outside world (for example, with TCP clients) continues smoothly after the move.
- The data storage location including the boot device used by the virtual machine must be active and accessible by both the source and destination ESX servers at all times.
- Access from vCenter Server and vSphere Client to both the ESX servers must be available to accomplish the migration.
Note: See Best practice documents in this article for additional requirements for VPLEX Distributed Virtual Volume.
Supported use cases for VMotion over Distance with VPLEX Metro
This table shows the supported cases with VPLEX configuration:
|
Case |
Support |
|
Simultaneous access to a shared Distributed Virtual Volume from two separate ESX clusters |
Supported |
|
VMotion between a host in ESX cluster 1/datacenter 1 to a host in ESX cluster 2/datacenter 2 leveraging the shared Distributed Virtual Volume |
Supported |
Tested Scenarios
When performing the VMotion over Distance over VPLEX Metro using Distributed Virtual Volume, the following failure scenarios are tested and supported.
Note: Boot from SAN configuration using Distributed Virtual Volume is not supported.
On creation of a VPLEX distributed volume, a winner VPLEX cluster must be assigned. In the event of VPLEX inter-cluster communication failure, the winner VPLEX cluster continues to service I/Os destined to the VPLEX distributed volume. The loser VPLEX cluster does not service I/Os received on the distributed volume.
The VPLEX behavior and impact on ESX servers are documented based on the fact that the VPLEX cluster at the source datacenter (Datacenter 1) is set as the winner for the VPLEX Distributed Virtual volume.
| Scenario | VPLEX Behavior | Impact on ESX hosts |
| Loss of ESX server at source | No impact. | Virtual machines that were running on the local ESX server can be registered and restarted on the destination ESX server. |
| Loss of ESX server at destination | No impact. | Virtual machines that were running on the remote ESX server can be registered and restarted on the source ESX server. |
| VPLEX cluster failure at source | I/O can be resumed on the VPLEX cluster at destination. | Virtual machines fail on ESX servers at both source and destination. They can be restarted on the destination ESX server. |
| VPLEX cluster failure at destination | VPLEX continues to process I/O at the source. When the VPLEX cluster at destination data center is back online, any changes written during the outage are replicated to the destination's Distributed volume mirror leg. | No impact to source ESX server. Virtual machines on destination ESX server fail. They can be restarted on the source ESX server. |
| Total Datacenter 1 failure (Total site failure) | I/O can be resumed on the VPLEX cluster at destination datacenter. | Virtual machines fail at destination ESX server. Virtual machines at source and destination ESX servers can be restarted on the destination ESX server. |
| Total Datacenter 2 failure (Total site failure) | VPLEX continues to process I/O at the source data center. When the VPLEX cluster at destination data center is back online, any changes written during the outage are replicated to the destination's Distributed volume mirror leg. |
VMotion fails with no interruption to source ESX. Virtual machines at destination ESX server can be restarted on the source ESX server with manual intervention. No impact on source ESX server. |
| Inter-site network failure (Network Partition) |
VPLEX winner cluster at Datacenter 1 continues to function. |
Destination ESX server is not able to perform I/O to VPLEX Distributed volumes. Manual intervention required to resume I/O at destination data center. No impact on source ESX server. |
| VPLEX inter-cluster communication link failure (Network Partition) |
VPLEX winner cluster at Datacenter 1 continues to function. |
Destination ESX server is not able to perform I/O to VPLEX Distributed Virtual Volumes. Manual intervention is required to resume I/O at destination. |
| VPLEX director failure |
No impact. I/O continues on the remaining directors. |
No impact. Under some conditions, a director failure may cause a VMotion that is already in progress to abort. However, the virtual machine continues to run at source and the VMotion can be re-initiated and completed as expected. |
| VPLEX management server failure | No impact. | No impact. |
| Redundant frontend path failure | No impact. | No impact. |
| Redundant backend path failure | No impact. | No impact. |
| Backend array failure on Datacenter 1 | No impact. VPLEX automatically starts rebuild when the failed Backend array is back. The rebuild may affect the host I/O response. The rebuild parameters can be adjusted to minimize the rebuild effect on host I/O response time. Contact EMC for more details. | ESX may observe slower I/O responses over Distributed Virtual Volume due to rebuilds. The rebuild parameters can be adjusted to minimize the rebuild effect on host I/O response time. Contact EMC for more details. |
| Backend array failure on Datacenter 2 | No impact. VPLEX automatically starts rebuild once the failed Backend array is back. The rebuild may affect the host I/O response. The rebuild parameters can be adjusted to minimize the rebuild effect on host I/O response time. Contact EMC for more details. | ESX may observe slower I/O responses over Distributed Virtual Volume due to rebuilds. The rebuild parameters can be adjusted to minimize the rebuild effect on host I/O response time. Contact EMC for more details. |
Best practice documents
The following EMC best practice documents for VMotion over Distance using VPLEX are available at EMC Powerlink:
- Implementation and Planning Best Practices for EMC VPLEX
- VMotion over Distance with EMC VPLEX Metro - Best Practices
Additional Information
This table defines terms used in this article:
| Term | Definition |
| Distributed Virtual Volume | A VPLEX virtual volume with complete, synchronized, copies of data (mirrors), exposed through 2 geographically separated VPLEX clusters. Distributed Virtual Volumes can be simultaneously accessed by servers at distant data centers thus allowing VMotion over Distance. |
| Winner Cluster | On creation of a VPLEX Distributed Virtual Volume, a winner VPLEX cluster must be assigned. In the event of VPLEX inter-cluster communication failure, the winner VPLEX cluster continues to service I/O destined to the VPLEX Distributed Virtual Volume. The loser VPLEX cluster does not service I/O received on the Distributed Virtual Volume. This VPLEX behavior addresses split-brain issues and data corruption in case of VPLEX inter-cluster network partition. |
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