Storage Volume Replication; Co-Located Replication Configurations - Seagate Exos X 4006 Series Hardware Installation And Maintenance Manual

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Storage volume replication

Storage volume replication is a licensed feature used for disaster recovery. It requires fibre channel (FC) or iSCSI SFP
connection. Typically, it involves two controller enclosures at different locations where a volume on the primary system uses
this feature to asynchronously replicate an internal snapshot of the primary volume to a volume on the secondary system. The
replication of block-level data involves a complete snapshot or copies the changes to the date since the last replication from
the primary to the secondary system.
If one of the controller modules in a control enclosure fails, the storage system fails over and runs on a single controller module
until you rectify the issue and restore redundancy.
There are several qualifiers to using storage volume replication:
You must obtain a license for both systems before you can use the replication feature.
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System controller modules must be compatible on all systems used for replication.
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Host ports used for replication must use the same protocol as the connected controllers: either FC or iSCSI.
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You cannot directly attach both systems. System controllers require connection through switches to the same fabric or
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network, whether the secondary system is remotely located or co-located with the primary system.
The two associated standard volumes form a replication set, where you can only access the primary or source volume.
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Connection is through the primary or source volume, but if the primary system goes offline, you can access the replicated
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date from the connected secondary system.
You must provide for a sufficient number of ports to perform replication. The primary system needs to balance the load
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across those ports as input and output demands rise and fall. If some of the replicated volumes connect to Controller 0A,
and others to Controller 0B, you need at least one port on each controller dedicated exclusively to replication. If you have a
heavy replication traffic load, you need more.
For remote replication instances, you must confirm that all ports designated and assigned for replication can properly
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communicate with the secondary system using the CLI command: query peer-connection.
The storage system does not provide for specific assignment of ports for replication. However, you can accomplish a
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similar function by using either iSCSI virtual LANs (VLANs) or FC zones or by using physically separate infrastructure.
For system security, do not expose network ports on controller enclosures to external network connections.
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Cabling for replication requires planning and thought. The samples included in this section are not exhaustive, but should
serve as an optimal, conceptual guideline for your custom system configuration.

Co-located replication configurations

Volume replication can occur on the same physical network, or on different physical networks. For situations where you need
to use a single physical network, you can logically separate networks by configuring fibre channel (FC) zones or iSCSI virtual
LANs (VLANs) to isolate input and output (I/O) traffic from replication traffic. In such a case, while such configurations
physically inhabit a single network, they logically function as multiple servers and networks.
Co-located replication with multiple switches and servers
Ideally, use three separate switches to avoid a single point of failure and allow for physical isolation of I/O traffic from
replication traffic. Two switches are dedicated to I/O traffic and act as the bridge to connect controller enclosures to multiple
host servers. The third switch is the replication switch and acts as the bridge to connect controller enclosures to each other.
Chapter 8 Storage enclosure management
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