Dell SRDF Introduction

SRDF/Star

SRDF/Star is a disaster recovery configuration that consists of three sites: primary (production), secondary, and tertiary. The secondary site synchronously mirrors the data from the primary site, and the tertiary site asynchronously mirrors the production data.

If an outage occurs at the primary site, SRDF/Star enables rapid transfer of operations to and re-establishment of remote mirroring between the remaining sites. When conditions permit, the primary site can rejoin the solution, resuming the SRDF/Star operations.

SRDF/Star operates in concurrent and cascaded configuration that address different recovery and availability objectives:

• Concurrent SRDF/Star—Data is mirrored from the primary site concurrently to two R2 devices. Both the secondary and tertiary sites are potential recovery sites should the primary site fail. Differential resynchronization is used between the secondary and the tertiary sites.
• Cascaded SRDF/Star—Data is mirrored first from the primary site to a secondary site, and then from the secondary to a tertiary site. Both the secondary and tertiary sites are potential recovery sites. Differential resynchronization is used between the primary and the tertiary site.

Differential synchronization between two remote sites:

• Allows SRDF/Star to rapidly reestablish cross-site mirroring should the primary site fail.
• Greatly reduces the time that is required to remotely mirror the selected production site.

If a rolling disaster affects the primary site, SRDF/Star helps in determining which remote site has the most current data. You can select which site to operate from and which site’s data to use when recovering from the primary site failure.

If the primary site fails, SRDF/Star enables resumption of asynchronous protection between the secondary and tertiary sites, with minimal data movement.