One system acts as the source and the other as a target in this replication pair (for example, acme-west and acme-east).When this type of relationship exists between distinct containers on two distinct DR Series systems, it can beconsidered bidirectional in the sense that:• The West1 container on the acme-west source system can replicate data to a separate East1 container on theacme-east target system.• The East2 container on the target acme-east system can also replicate data back to the West2 container on thesource acme-west system.This form of replication involves separate containers on two distinct DR Series systems. Target containers in replicationmust always act as read-only, while sources containers can act as read-write. Unlike NFS and CIFS containers, OSTcontainer replication is handled by the supported Data Management Applications (DMAs) on the corresponding mediaservers. For details, see Understanding OST.The DR Series system supports the 32:1 replication of data, whereby up to 32 source DR Series systems can write datato different individual containers on a single, target DR Series system. This supports the use case where branch orregional offices can each write their own data to a separate, distinct container on a main corporate DR Series system.NOTE: Be aware that the storage capacity of the target DR Series system is directly affected by the number ofsource systems writing to its containers, and by the amount being written by each of the source systems.However, if the source and target systems in a replication pair are in different Active Directory (AD) domains, then thedata that resides on the target system may not be accessible. When AD is used to perform authentication for DR Seriessystems, the AD information is saved with the file. This can act to restrict user access to the data based on the type ofAD permissions that are in place.NOTE: This same authentication information is replicated to the target DR Series system when you have replicationconfigured. To prevent domain access issues, ensure that both the target and source systems reside in the sameActive Directory domain.Reverse ReplicationThe concept of reverse replication is not a supported operation on DR Series systems. This is because replicacontainers are always in a R-O (read-only) mode on the DR Series system, thus making write operations a non-supported operation.Under very specific conditions, it might be possible for replica containers to support a type of write operation whosesole function is to restore data from an archival target. For example, data could be replicated back to the remote sitewhere a data management application (DMA), or backup software, is connected to allow this data to be restoreddirectly.This specific type of case applies only to configurations where data is backed up from a remote location to a localcontainer, and then replicated over a WAN to a replica container that is backed up to tape. The data needs to berestored from the tape backup to the original location; first back to a DR Series system replica container, and then backto the original source location of the data on the other side of the WAN link.NOTE: If you choose to use this alternate workaround method, you must set up a new data storage unit in the DMA,and import the images before a restore to the original location can occur.To leverage this type of deduplication across the WAN, complete the following:1. Make sure that the replication operation has completed (between source and target).2. Delete the current replication relationship, and re-create a replication relationship (reversing the source and targetroles).3. Restore data to the original source container (now the target).4. Make sure that the replication operation has completed.18
