Data Domain Extended Retention

Data Domain Extended Retention is the new name for Data Domain Archiver.  It is a licensed software feature which supports VTL and MTree, as well as CIFS and NFS data.  It also utilizes "Fast Seeding" which improves data migration from the active to retention tiers of storage, and "packing" which reclaims duplicate segments in the retention tier.  Deduplication takes place only within a specific tier, not across active and retention tiers.

Extended Retention is supported only on the DD860 and DD990 and with the ES20 or ES30 expansion cabinets.

The benefits of ER are that data can be written to the active tier very quickly and then moved off to slower retention tiers as time permits.  The active tier will typically hold data for 90 days or less, with the retention tiers holding data as long as policy requires.  There is also a high data ingress rate (up to 31TB/hour), and the cost per GB goes down drastically as the system scales with more expansion shelves.

The retention tier is made up of several retention units.  Each unit can span multiple shelves if configured to do so, or can be portions of shelves.  Data moves out of the active tier into the first retention unit until that unit is completely full.  Once full, the unit is "sealed" and the second unit is started until it is full, etc.  This way, oldest data is in one retention unit, followed by the next and the next.  Deduplication takes place only in each unit to reduce the likelihood of losing multiple units should there be a failure.  This is the Fault Isolation of Data Domain, as well.

All data on a DD Extended Retention system appears active.  Tiering is transparent.  To accommodate scalability, not all retention units are readily available in memory.  Oldest data will be de-prioritized and put on standby but is still more accessible than tape.  Data can also be replicated from one DD ER unit to another using collection replication, which replicates the entire box with each tier in place.