This article provides information about deploying a Metro Storage Cluster across two datacenters using EMC VPLEX Metro 5.0. With vSphere 5.0, a Storage Virtualization Device can be supported in a Metro Storage cluster configuration.

What is VPLEX?

EMC VPLEX is a federation solution that provides simultaneous access to storage devices at two geographically separate sites. One or more VPLEXDistributedVirtual Volumes can be provisioned for sharing between the two sites’ ESXi hosts. These volumes can be used asRaw Device Mapping (RDM) disks or as a shared VMFS datastore. The RDM can be used for exclusive access by the virtual machine and the VMFS datastore can be used for provisioning virtual machines and carving out additional vDisks.

The VPLEX cluster at each site itself is designed to be highly available. A VPLEX cluster can scale from two directors to eight directors. Each director is protected by redundant power supplies, fans, and interconnects, making the VPLEX highly resilient.

What is vMSC?

vSphere Metro Storage Cluster (vMSC) is new configuration. A storage device configured in the MSC configuration is supported after successful vMSC certification. All supported storage devices are listed on the VMware Storage Compatibility Guide.

VPLEX Witness

VPLEX Witness is a VPLEX component provisioned as a virtual machine on an ESXi host that is typically deployed at a third site. Deploying a VPLEX Metro Solution with VPLEX Witness gives continuous availability to the storage volumes in case of a site failure or inter-cluster link failure.

When a VPLEX Distributed Virtual Volume is provisioned, a per volume preferred site flag may be enabled orDistributed Virtual Volumes with the same preferred site settings may be placed in the same consistency group.The preference criteria can be things like the availability, presence of monitoring staff, or location.VPLEX Witness failure handling semantics apply only to the Distributed Virtual Volumes within a consistency group.

Configuration Requirements

These requirements must be satisfied to support this configuration:

  • The maximum round trip latency on both the IP network and the inter-cluster network between the two VPLEX clusters must not exceed 5 milliseconds round-trip-time for a non-uniform host access configuration and must not exceed 1 millisecond round-trip-time for a uniform host access configuration. The IP network supports the VMware ESXi hosts and the VPLEX Management Console. The interface between two VPLEX clusters can be Fibre Channel or IP.
  • The ESXi hosts in both data centers must have a private network on the same IP subnet and broadcast domain.
  • Any IP subnet used by the virtual machine that resides on it, must be accessible from ESXi hosts in both datacenters. This requirement is important so that clients accessing virtual machines running on ESXi hosts on both sides are able to function smoothly upon any VMware HA triggered virtual machine restart events.
  • The data storage locations, including the boot device used by the virtual machines, must be active and accessible from ESXi hosts in both datacenters.
  • vCenter Server must be able to connect to ESXi hosts in both datacenters.
  • The VMware datastore for the virtual machines running in the ESX Cluster are provisioned on Distributed Virtual Volumes.
  • The maximum number of hosts in the HA cluster must not exceed 32 hosts.
  • The configuration option auto-resume for VPLEX consistency groups must be set to true.

Notes:

  • The ESXi hosts forming the VMware HA cluster can be distributed on two sites. HA Clusters can start a virtual machine on the surviving ESXi host, and the ESXi host access the Distributed Virtual Volume through storage path at its site.
  • VPLEX 5.0 and ESXi 5.0 are tested in this configuration with the VPLEX Witness.

For any additional requirement for VPLEX Distributed Virtual Volumes, see the EMC VPLEX best practices document.

Solution Overview

A VMware HA/DRS cluster is created across the two sites using ESXi 5.0 hosts and managed by vCenter Server 5.0. The vSphere Management, vMotion, and virtual machine networks are connected using redundant a network between the two sites. It is assumed that the vCenter Server managing the HA/DRS cluster can connect to the ESXi hosts at both sites. This diagram provides an overview:
Based on the host SAN connections to the VPLEX storage cluster, there are two different types of deployments possible:
  • Non-uniform Host Access – This type of deployment involve the hosts at either site see the storage volumes through the same site storage cluster only. This diagram provides an example:
  • Uniform Host Access (Cross-Connect) – This deployment involve establishing a front-end SAN across the two sites, so that the hosts at one site could see the storage cluster at the same site as well as the other site.  These best practices must be followed for this type of deployment:
    • The front-end zoning should be done in such a manner that an HBA port is zoned to either the local or the remote VPLEX cluster.
    • The path policy should be set to FIXED to avoid writes to both legs of the distributed volume by the same host.
This diagram provides an example:
A VPLEX Metro solution federated across the two datacenters provides the distributer storage to the ESXi hosts. It is assumed that the ESXi boot disk is located on the internal drives specific to the hosts and not on the Distributed Virtual Volume itself.
The virtual machine is ideally run on the preferred site of the Distributed Virtual Volume.
More details on VMware KB
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