This e-Learning module will help you learn more about several types of remote mirror and Copy Services offered with the IBM(R) DS8000(R) series. These advanced two-site and three-site business continuity capabilities can enable your mission-critical applications to be available when you need them during both planned and unplanned system outages. Remote mirror and Copy Services features help administrators migrate, back up, and recover data by creating synchronous and asynchronous copies of volumes.
Remote mirror and Copy Services include: Metro Mirror, Global Copy, and Global Mirror. Also available is Multi Target Mirror. We will look at each in more detail.
Similar to FlashCopy(R), all of these services copy a source volume to a target volume. But, unlike FlashCopy, the source and target volumes can be located some distance from each other. This allows a backup to be kept at a farther physical location. And, while FlashCopy creates a single point-in-time copy, remote mirroring and Copy Services copy all changes that are made on the source volume.
Metro Mirror is a copy service that provides a continuous, synchronous mirror of one volume to a second volume. The different volumes can be up to 300 kilometers apart, so by using Metro Mirror you can make a copy to a location offsite or across town. Because the mirror is updated in real time, no data is lost if a failure occurs. Metro Mirror is generally used for disaster recovery purposes, data protection, data vaulting, and high availability. Metro Mirror can be implemented when both the source and target locations are on the same SAN or when they are on separate, remote SANs, without having to use channel extenders.
Global Copy, just like Metro Mirror, is a copy service that provides an mirror of a set of volumes to a remote location. But Global Copy is asynchronous, with host write operations to the target site considered complete before they are transmitted to a storage unit at the target site. This reduced write latency and more efficient use of bandwidth make Global Copy a good option for migrating large amounts of data or moving non-production-critical data to recovery sites that are more than 300 kilometers away.
Global Mirror consists of one or more Global Copy relationships, so the volumes can be located more than 300 kilometers apart. With Global Mirror, the target Global Copy volume has a FlashCopy relationship with a third volume. This means that the source system does not have to wait for verification from the target system, which enables faster synchronization without draining performance. Global Mirror can help reduce recovery time to less than five seconds, which is important for mission-critical applications. However, unlike Metro Mirror, if a failure occurs, you might lose the data in transmission when the outage occurs.
Multi-Target Mirror replicates data from a single primary site to two secondary sites. This builds upon and extends Metro Mirror and Global Mirror. Synchronous replication, asynchronous replication, and a combination of both synchronous and asynchronous are available. Failure at one secondary site does not affect the capability of the other site. The result is increased capability and flexibility in disaster recovery solutions. In the event of an outage at the primary site, control can be moved to either secondary site. Multi-Target Mirror provides for an incremental resynchronization between the two secondary sites to quickly restore high availability and disaster recovery capability.
To access the Metro Mirror or Global Copy functions that were just described, you first need to create a path between logical subsystems (or LSSs) in the source and target storage units. Then, you need to create a relationship between the source and target volumes.
To learn more about the remote copy and mirroring features, and how to perform advanced tasks, see additional topics in Knowledge Center.