512 Implementing the IBM Storwize V5000
򐂰 ConsistentDisconnected
The volumes in this half of the consistency group are all operating in the secondary role
and can accept read I/O operations but not write I/O operations.
򐂰 Empty
The consistency group does not contain any relationships.
10.2.3 Remote Copy planning
Before you use Remote Copy, you must plan for its usage.
General guidelines for Remote Copy
General guidelines for Remote Copy include the following considerations:
򐂰 Partnerships between up to four IBM Storwize V5000 storage systems, IBM SAN Volume
Controller systems, IBM Storwize V7000, or IBM Storwize V3700 is allowed. The
partnership must be defined on any partnered IBM Storwize storage systems or IBM SAN
Volume Controller systems to make it fully functional.
򐂰 The two volumes in a relationship must be the same size.
򐂰 The Remote Copy relationship can be established on the volumes within one IBM
Storwize V5000 storage system or in different IBM Storwize V5000 storage systems.
When the two volumes are in the same cluster, they must be in the same I/O group.
򐂰 You cannot use Remote Copy target volumes as Remote Copy source volumes. However,
a FlashCopy target volume can be used as Remote Copy source volume. Other
restrictions are outlined in Table 10-5 on page 514.
򐂰 The Metro Mirror function supports copy operations between volumes that are separated
by distances up to 300 km.
򐂰 One Remote Copy relationship can belong only to one consistency group.
򐂰 All relationships in a consistency group must have matching primary and secondary
clusters, (master clusters and auxiliary clusters). All relationships in a consistency group
must also have the same copy direction and state.
򐂰 Metro Mirror and Global Mirror relationships cannot belong to the same consistency
group.
򐂰 To manage multiple Remote Copy relationships as one entity, relationships can be made
part of a Remote Copy consistency group, which ensures data consistency across
multiple Remote Copy relationships and provides ease of management.
򐂰 An IBM Storwize V5000 storage system implements flexible resynchronization support,
which enables it to resynchronize volume pairs that experienced write I/Os to both disks
and to resynchronize only those regions that are known to changed.
򐂰 Global Mirror with Change Volumes should have Change Volumes that are defined for the
master and auxiliary volumes.
Chapter 10. Copy services 513
Remote Copy configuration limits
Table 10-4 lists the Remote Copy configuration limits.
Table 10-4 Remote Copy configuration limits
SAN planning for Remote Copy
In this section, we describe some guidelines that can be used for planning for a SAN for
Remote Copy.
Zoning recommendation
Node canister ports on each IBM Storwize V5000 must communicate with each other so that
the partnership can be created. These ports must be visible to each other on your SAN.
Proper switch zoning is critical to facilitating inter-cluster communication.
The following SAN zoning recommendation should be considered:
򐂰 For each node canister, exactly two Fibre Channel ports should be zoned to exactly two
Fibre Channel ports from each node canister in the partner cluster.
򐂰 If dual-redundant inter-switch links (ISLs) are available, the two ports from each node
should be split evenly between the two ISLs; that is, exactly one port from each node
canister should be zoned across each ISL. For more information, see this website:
http://www-01.ibm.com/support/docview.wss?uid=ssg1S1003634&myns=s033&mynp=famil
yind5329743&mync=E
򐂰 All local zoning rules should be followed. A properly configured SAN fabric is key to not
only local SAN performance, but Remote Copy. For more information about these rules,
see this website:
http://publib.boulder.ibm.com/infocenter/storwize/ic/index.jsp?topic=%2Fcom.ibm
.storwize.V5000.doc%2Fsvc_configrulessummary_02171530.html
Remote Copy link requirements
The following link requirements are valid for Metro Mirror and Global Mirror:
򐂰 Round-trip latency
The total round-trip latency must be less than 80 ms and less than 40 ms in each direction.
Latency simulations should be performed with your applications before any network links
are put in place to see whether the applications perform at an acceptable level while they
meet the round-trip latency requirement.
Parameter Value
Number of Remote Copy consistency groups per cluster 256
Number of Remote Copy relationships per consistency group 8,192
Number of Remote Copy relationships per I/O Group 2,048
Total Remote Copy volume capacity per I/O Group 1024 TB
(This limit is the total capacity for
all master and auxiliary volumes in
the I/O group.)
Fabrics: When a local fabric and a remote fabric are connected for Remote Copy
purposes, the ISL hop count between a local node and a remote node cannot exceed
seven.

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