SRDF/Data Mobility

SRDF/Data Mobility (SRDF/DM)
SRDF/DM is a data migration/data mobility solution that enables fast data transfer from R1 to R2 devices over extended distances.
SRDF/Data Mobility (SRDF/DM) operates in only SRDF adaptive copy mode and is designed for data replication or migration between two or more Symmetrix arrays. SRDF adaptive copy mode provides a fast application response time. SRDF/DM is supported on all Symmetrix hardware models and all Enginuity versions that support SRDF, and can be used for local or remote transfers.


The SRDF adaptive copy modes allow the R1 and R2 devices to be more than one write I/O and up to the maximum skew value out of synchronization. By default, the maximum skew value is set to 65535 tracks. Once the maximum skew value is reached, the SRDF emulations must start the synchronization process to transfer updates across the SRDF links from the R1 to the R2 devices.



Adaptive copy modes
You can set the maximum skew value at the device level by using the EMC host-based SRDF software. Adaptive copy is supported as the secondary mode of operation to synchronous or semi-synchronous mode. The R1 devices revert to the primary mode of operation when the maximum skew value is reached and remain in primary mode until the number of tracks out of synchronization is lower than the maximum skew value.

You can set the maximum skew value at the device level by using the EMC host-based SRDF software. Adaptive copy is supported as the secondary mode of operation to synchronous or semi-synchronous mode. The R1 devices revert to the primary mode of operation when the maximum skew value is reached and remain in primary mode until the number of tracks out of synchronization is lower than the maximum skew value.

Adaptive copy write pending
In SRDF adaptive copy write pending mode, write requests accumulate in cache in the primary array. A background process writes to the corresponding R2 device on the other side of the SRDF links.

Note: SRDF adaptive copy write-pending mode reverts to the specified primary mode if 75% of the write pending limit for the Symmetrix array is reached, regardless of whether the maximum skew value specified for each device is reached.


Adaptive copy disk
In SRDF adaptive copy disk mode, the write requests accumulate on the R1 device rather than in Symmetrix cache. A background process sends the outstanding write requests to the corresponding R2 device.
With Enginuity version 5773 or higher, the background copy process scheduled to send I/Os from the R1 to the R2 devices can be deferred if:

  •  The write requests exceed the maximum R2 write pending limits.
  •  The write requests exceed 50 percent of the secondary array write pending space.

 

SRDF/Data Mobility
SRDF/Data Mobility (SRDF/DM) is a licensed two-site SRDF data migration and replication solution that only operates in adaptive copy modes. The maximum skew value set at the device level in SRDF/DM solutions must be equal or greater than 100 tracks.