HP XP Racks - Manual (Page 3)

Contents
1 Continuous Access Synchronous overview......................................................7
How Continuous Access Synchronous works ................................................................................7
Typical components .................................................................................................................8
Storage systems .......................................................................................................................8
Volume pairs ...........................................................................................................................9
Data path ...............................................................................................................................9
Consistency groups ..................................................................................................................9
Interfaces ................................................................................................................................9
Failover software ...................................................................................................................10
Overview of initial, update copy operations ..............................................................................10
Initial copy .......................................................................................................................10
Update copy ....................................................................................................................10
Pair status..............................................................................................................................11
2 Requirements and specifications.................................................................12
System requirements and specifications......................................................................................12
3 Planning for Continuous Access Synchronous...............................................15
Storage system preparation......................................................................................................15
Cache, additional shared memory requirements.....................................................................15
Requirements for XP7 with earlier model storage systems.........................................................15
System options...................................................................................................................16
System performance considerations...........................................................................................16
Determining Round Trip Time...............................................................................................16
Determining Minimum Number of Remote Paths.....................................................................18
Analyzing workload, planning data paths.............................................................................18
Planning pairs and pair volumes...............................................................................................19
Pair volume requirements and recommendations....................................................................19
About allowing I/O to the S-VOL.........................................................................................20
Allowing I/O to the P-VOL after a split—Fence Level options....................................................20
Differential data ................................................................................................................21
Maximum number of pairs supported...................................................................................21
Calculating maximum number of pairs.............................................................................21
Priority for initial copy operations and scheduling order..........................................................23
Example 1: more initial copies than previously specified.....................................................23
Example 2: initial copy started, new pairs added..............................................................24
Consistency group planning.....................................................................................................24
Consistency group for pairs in one primary and one secondary XP7........................................24
Consistency group for pairs in multiple primary and secondary systems....................................25
Consistency group requirements ..........................................................................................26
Requirements for a CTG for one primary and one secondary system....................................26
Requirements for a CTG for multiple primary and secondary systems....................................26
Assigning pairs to a consistency group.................................................................................27
Assigning pairs belonging to one primary and secondary system........................................27
Assigning pairs belonging to multiple primary and secondary systems.................................27
Split behaviors for pairs in a CG..........................................................................................28
Host access after split....................................................................................................29
Pair status before and after a split operation.....................................................................30
Consistency group 127.......................................................................................................30
CG 127 behavior and restrictions when a pair is suspended...............................................31
CG 127 behavior and restrictions when the data path fails.................................................31
Notes when you remove or resynchronize pairs by Business Continuity Manager........................32
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