single remote replication session or multiple remote replication sessions in a consistency
group at one time. A primary/secondary switchover is typically performed in the following
scenarios:
l
After the primary site recovers from disasters, the remote replication links are
reestablished and data is synchronized between the primary and secondary sites.
l
When the primary storage system requires maintenance or an upgrade, the secondary
storage system must take control of services.
After a primary/secondary switchover, services run on the secondary storage system instead.
Data on the secondary LUN must be available prior to the primary/secondary switchover.
Determine whether data on the secondary LUN is available by viewing its data status.
Data Status
By determining differences between a primary and a secondary LUN, remote replication
identifies the data status of the current pair. If a disaster occurs, remote replication determines
whether to allow a primary/secondary switchover based on the data status of the pair. The
acceptable data states are
Consistent
and
Inconsistent
.
Writable Secondary LUN
Hosts can send data to secondary LUNs. By default, the secondary LUN can only be read
following configuration of remote replication. If the primary LUN fails, set
Status of
Secondary Resource Protection
to
Read/Write
. This allows writing to the secondary LUN
and ensures service continuity by allowing the secondary storage system to maintain host
services. You must configure the secondary LUN to be writable in the following scenarios:
l
The primary LUN fails and the remote replication link is in the disconnected state.
l
The primary LUN fails and the remote replication link is in the normal state. The pair
must be split before you enable the secondary LUN to be writable.
Link Compression
In an asynchronous remote replication task, data is compressed on the primary storage system
before transfer. That data is decompressed on the secondary storage system, reducing
bandwidth use in data transfer. Link compression on the OceanStor storage systems provides
the following advantages:
l
Inline data compression
Data is compressed when being transferred.
l
Intelligent compression
The system preemptively determines if data can be compressed, preventing unnecessary
compression and improving transfer efficiency.
l
High reliability and security
Lossless compression technology is used to ensure data security. Multiple check methods
ensure data reliability. After receiving data, the secondary device verifies data
correctness and checks data integrity after the data is decompressed.
l
User unawareness
Link compression does not affect services running on the host and is transparent to users.
l
Compatibility with full backup and incremental backup
Link compression compresses all data that is transferred over the network regardless of
upper-layer services.
OceanStor V3 Series
Remote Replication Feature Guide for Block
1 Feature Description
Issue 06 (2018-01-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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