SFW 6.1: Support for Cluster Volume Manager (CVM)

[Anand_Mehta]

Cluster Volume Manager (CVM) is a new feature introduced in Symantec Storage Foundation for Windows (SFW) 6.1. CVM is a new way to manage storage in a clustered environment. With CVM, failover capabilities are available at the volume level.

Volumes under CVM allow exclusive write access across multiple nodes of a cluster. In a Microsoft Failover Clustering environment, you can create clustered storage out of shared disks, which lets you share volume configurations and enable fast failover support at the volume level. Each node recognizes the same logical volume layout and, more importantly, the same state of all volume resources. Each node has the same logical view of the disk configuration as well as any changes to this view.

Note: CVM (and related cluster-shared disk groups) is supported only in a Microsoft Hyper-V environment. It is not supported for a physical environment.

CVM is based on a "Master and Slave" architecture pattern. One node of the cluster acts as a Master, while the rest of the nodes are Slaves. The Master node maintains the configuration information. The Master node uses Global Atomic Broadcast (GAB) and Low Latency Transport (LLT) to transport its configuration data. Each time a Master node fails, a new Master node is selected from the surviving nodes.

With CVM, storage services on a per virtual machine (VM) basis for Hyper-V virtual machines protects VM data from single LUN/array failures, helping maintain availability of the critical VM data.

CVM helps you achieve the following:

• Live migration of Hyper-V virtual machines, which is supported with the following:
  • Virtual Hard Disks (VHDs) of virtual machine lying on one or more SFW volumes
  • Coexistence with Cluster Shared Volumes (CSV)
  • Mapping of one cluster-shared volume to one virtual machine only
• Seamless migration between arrays
  • Migration of volumes (hosting VHDs) from any array to another array
• Easy administration using the Storage Migration Wizard
  • Moving of the selected virtual machines’ storage to new target LUNs
  • Copying of only those NTFS blocks that contain user data using SmartMove
  • Availability of all the volume management functionality

The following are the main features supported in CVM:

• New cluster-shared disk group (CSDG) and cluster-shared volumes
• Disk group accessibility from multiple nodes in a cluster where volumes remain exclusively accessible from only one node in the cluster
• Failover at a volume level
• All the SFW storage management features, such as:
  • SmartIO
  • Thin provisioning and storage reclamation
  • Symantec Dynamic Multi-Pathing for Windows (DMPW)
  • Site-aware allocation using the site-aware read policy
  • Storage migration
  • Standard features for fault tolerance: mirroring across arrays, hot relocation, dirty region logging (DRL), and dynamic relayout
• Microsoft Failover Clustering integrated I/O fencing
• New Volume Manager Shared Volume resource for Microsoft failover cluster
• New GUI elements in VEA related to the new disk group and volume

CVM does not support:

• Active/Passive (A/P) arrays
• Storage migration on volumes that are offline in the cluster
• Volume replication on CVM volumes using Symantec Storage Foundation Volume Replicator

For information about configuring a CVM cluster, refer to the quick start guide at:

www.symantec.com/docs/DOC8119

The Storage Foundation for Windows documentation for other releases and platforms can be found on the SORT website.