Dell SRDF Introduction

Virtual Witness (vWitness)

vWitness has similar capabilities to the Array Witness. However, instead of running on an array, vWitness runs as a daemon on a Linux host, or as a virtual appliance (vApp) on a VMware ESXi server. The run-time environment of the vWitness depends on the version of the SRDF/Metro storage arrays. Arrays that run PowerMaxOS 6079.xxx.xxx use vWitnesses that run as a daemon. Previous versions of PowerMaxOS 5978 and HYPERMAX OS 5977 can use either type of vWitness.

For redundancy, there can be up to 32 vWitnesses.

The management guests on the R1 and R2 arrays maintain multiple IP connections to redundant vWitness instances. These connections use TLS/SSL for secure connectivity.

After creating IP connectivity to the arrays, the storage administrator can use SRDF management software to:

• Add a vWitness to the configuration. This action does not affect any existing vWitnesses. Once the vWitness is added, it is available to participate in the vWitness infrastructure.
• Query the state of a vWitness configuration.
• Suspend a vWitness. If the vWitness is servicing an SRDF/Metro session, this operation requires a force flag. The SRDF/Metro session is in an unprotected state until it renegotiates with another witness, if available.
• Remove a vWitness from the configuration. Once the vWitness is removed, SRDF/Metro breaks the connection with vWitness. The administrator can only remove vWitnesses that are not servicing active SRDF/Metro sessions. Also, the administrator cannot remove a vWitness when there is no alternative Witness (array or vWitness) for the SRDF/Metro configuration to use.