Administrator Guide

• Disconnect the SyncActive volume, as documented in the Group Manager online help. If the disconnect fails, try logging in
to a dierent member in the SyncActive pool.
NOTE: If the disconnect operation will not succeed from any member in the SyncActive pool, contact your Dell
support provider for assistance.
• Log in to the Group Manager GUI using an IP address that belongs to a group member in the pool containing the
SyncAlternate volume. Do not use the group IP address.
• Fail over the volume.
5. Set the volume back online, restoring initiator access. The new SyncActive volume (formerly SyncAlternate) accepts writes and
tracks changes made while the original SyncActive volume is oine. Depending on host conguration and application
requirements, you might have to restart hosts that were connected to the volume.
6. After access to the volume has been restored, the system performs the following steps:
a. When the original SyncActive volume is available again, it becomes the SyncAlternate volume.
b. Synchronous replication resumes. The volume is out of sync, and tracked changes are written to the new SyncAlternate
volume.
c. When the volume becomes in sync again, new writes are simultaneously written to both pools. You can switch back to the
original pool conguration, or continue using the new pool conguration.
Requirements for Using Synchronous Replication
Before you can congure a volume to use synchronous replication, verify that the following requirements are met:
• Two pools, each containing at least one member
• Adequate network bandwidth between pools
• Free space in each pool to accommodate the volume and snapshot reserve for the volume
Also note the following restrictions:
• You cannot enable synchronous replication on a volume for which traditional replication is congured, and you cannot enable
traditional replication on a volume for which synchronous replication is congured.
• You cannot enable synchronous replication on a volume that is bound to a group member. See About Overriding Automatic Load
Balancing for more information about binding and unbinding volumes.
• To support up to 32 volumes for synchronous replication, a PS Series group must contain only PS6cxx0 arrays. If the group
contains one or more PS4xx0 arrays, only 4 volumes are supported.
Synchronous Replication States
Synchronous replication states for a volume include:
• in sync
SyncActive and SyncAlternate copies of a volume contain the same data.
• paused
Administrator has paused synchronous replication. While synchronous replication is paused, the volume is still online, and initiators
can connect to and write to the SyncActive volume.
An administrator might pause and later resume synchronous replication. For example, this situation could happen in a
maintenance window during which the SyncAlternate volume is taken oine. If data is written to the volume while synchronous
replication is paused, it is written only to the SyncActive volume, and the two volumes are out of sync. The group tracks all
volume writes while synchronous replication is paused and, when the administrator resumes synchronous replication, writes the
tracked changes to the SyncAlternate volume.
• out of sync
SyncActive volume and SyncAlternate volume might not contain the same data; the SyncActive volume contains the most
recent data.
About Synchronous Replication
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