Home > Storage > PowerMax and VMAX > Data Protection > Dell PowerMax: Reliability, Availability, and Serviceability > Remote replication using SRDF
Symmetrix Remote Data Facility (SRDF) solutions provide industry-leading disaster recovery and data mobility solutions. SRDF replicates data between two, three, or four arrays located in the same room, on the same campus, or thousands of kilometers apart.
SRDF disaster recovery solutions use “active remote” mirroring and dependent-write logic to create consistent copies of data. Dependent-write consistency ensures transactional consistency when the applications are restarted at the remote location. SRDF can be tailored to meet various Recovery Point Objectives/Recovery Time Objectives.
SRDF can be used to create complete solutions to:
SRDF integrates with other Dell Technologies products to create complete solutions to:
Cascaded SRDF configurations use three-site remote replication with SRDF/A mirroring between sites B and C, delivering additional disaster restart flexibility.
Figure 19 shows an example of a Cascaded SRDF solution.
SRDF/Star is commonly used to deliver the highest resiliency in disaster recovery. SRDF/Star is configured with three sites enabling resumption of SRDF/A with no data loss between the two remaining sites, providing continuous remote data mirroring and preserving disaster-restart capabilities.
Figure 20 shows examples of Cascaded and Concurrent SRDF/Star solutions.
SRDF/Metro significantly changes the traditional behavior of SRDF Synchronous mode with respect to the remote (R2) device availability to better support host applications in high-availability environments. With SRDF/Metro, the SRDF R2 device is read/write accessible to the host and takes on the federated (such as geometry and device WWN) personality of the primary R1 device. By providing this federated personality on the R2 device, both R1 and R2 devices then appear as a single virtual device to the host. With both the R1 and R2 devices being accessible, the host or hosts (in the case of a cluster) can read and write to both R1 and R2 devices with SRDF/Metro ensuring that each copy remains current, consistent, and addressing any write conflicts that may occur between the paired SRDF devices.
Figure 21 shows examples of SRDF/Metro solutions.
On the left is an SRDF/Metro configuration with a stand-alone host that has read/write access to both arrays (R1 and R2 devices) using multipathing software such as PowerPath. This is enabled by federating the personality of the R1 device to ensure that the paired R2 device appears, through additional paths to the host, as a single virtualized device.
On the right is a clustered host environment where each cluster node has dedicated access to an individual array. In either case, writes to the R1 or R2 devices are synchronously copied to its SRDF paired device. Should a conflict occur between writes to paired SRDF/Metro devices, the conflicts are internally resolved to ensure a consistent image between paired SRDF devices is maintained to the individual host or host cluster.
SRDF/Metro may be selected and managed through Solutions Enabler, Unisphere for PowerMax, and REST API. SRDF/Metro requires a separate license on both arrays to be managed.