Functions Of A Consistency Group - Huawei OceanStor V3 Series Features Manual

OceanStor V3 Series
Remote Replication Feature Guide for Block
Figure 1-5 Process of data recovery at the primary site following a disaster

1.3.5 Functions of a Consistency Group

In medium- and large-sized database applications, data, logs, and modification information
are stored on different LUNs that have relationships with each other. If data on one of the
LUNs becomes unavailable, data on the other LUNs also becomes unavailable. Adding LUN
pairs to a consistency group ensures the availability of data on the LUNs. This section
compares storage systems running a consistency group with storage systems not running a
consistency group to show you how a consistency group ensures business continuity.
Issue 06 (2018-01-30)
Primary site
Production
host
Secondary
LUN
Primary storage
system
Production
host
Secondary
LUN
Primary storage system
Production
host
The
production
host runs
services.
Primary
LUN
Primary storage system
NOTE
In asynchronous remote replication scenarios, the storage system performs data synchronization until
data differences between the primary and secondary LUNs are minimal. The storage system then stops
services and performs the final synchronization. This prevents data loss and minimizes downtime.
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Secondary site
Standby host
Links restored
Secondary storage
system
Standby host
Recovers data
New remote replication
links
Secondary storage system
Standby host
Remote replication
Secondary storage system
1. The primary site recovers from the
·
The primary storage system recovers
from the disaster. And the links
between storage systems are
restored.
The standby ·
After the links are restored, it is
host runs
need to perform a primary/secondary
switchover manually on the primary
services.
site, to make the secondary LUN on
the secondary storage system
Primary
LUN become the primary one.
2. The secondary site recovers data at the
primary site.
·
Synchronous: Perform synchronization
once to copy data on the primary LUN
to the secondary LUN.
·
Asynchronous: Perform
synchronization for multiple times
during idle hours to copy data on the
primary LUN to the secondary LUN.
Primary
LUN
3. The primary site recovers services.
·
Synchronous: Perform a
primary/secondary switchover to
restore the pre-disaster pair.
·
Asynchronous: Start synchronization
again to eliminate the difference
caused by host writes during the
previous synchronization. Then split
Pair to set the secondary LUN to be
writable and perform a
Secondary
primary/secondary switchover to
LUN
restore the pre-disaster pair.
·
After recovered the pair, set the
secondary resource protection status
to read-only in the primary storage
system.
1 Feature Description
disaster.
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