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Continuous Access Overview
Damian McNamaraConsultant
Continuous Access (1)
CA copies data online and in real time using synchronous replication to remote locations through a local or extended SAN
Database Mirror
Database
Continuous Access (2)
Host is not aware of remote locationHost writes its data to a LUN
Database Mirror
Database
Continuous Access (3)
Source controller writes data in its cacheCA EVA copies data to remote controllers cache
Database Mirror
Database
Continuous Access (4)
Remote controller sends ACK to local controllerRemote host writes data to a data disk
Database Mirror
Database
Continuous Access (5)
• Local controller informs host that I/O is completed
Database Mirror
Database
Continuous Access EVA
Copy Set
Copy Set
Dest
VOL
DestVOL
Source
VOL
SourceVOL
Remote copying
• What does it do?– Replicates LUNs between EVAs– Provides disaster recovery– Simplifies workload management– Allows point-in-time database
backup– Provides restore without latency
• Business drivers– Creates up to 128 Copy Sets for
all specified logical units in the array over Fibre Channel and FC extensions
– Synchronous and asynchronous support up to 20’000km (200ms round trip time)
– Works with all EVAs
DR groups and managed sets
DR Group• Consistent Group of replicated copy sets
(Vdisks)– Up to 32 replicated copy sets per DR Group– IO ordering across members is guaranteed– Share a single write history log– Vdisks within a DR Group behave like a single entity– Management commands like suspend or failover are
handled atomicaly– All source members online on same HSV controller
• Therefore a DR Group is the primary level of CA management
– Write Mode ([Synchronous] / Asynchronous)– Failsafe Mode (Enabled or [Disabled])– Suspend Mode ([Resume] / Suspend)– Failover command
Managed Sets• Another level of CA management
– Collection of DR groups for the purpose of common management
– No consistency as between members of a DR Group– If you perform a management command on a
Managed Set this command will be run for all contained DR Group one after the other
Vdisk
DR Group
Managed Set
Multiple relationships
• Fan-in of multiple relationships– The ability of one EVA to act as the
destination for different LUNs from more than one source EVA
• Fan-out of multiple relationships– The ability for different LUNs on
one EVA to replicate to different destination EVA
• Bidirectional– one array with copy sets acting as
the source and destination across the same intersite links or fabric
EVA8000
EVA5000
EVA3000
EVA5000
EVA4000
EVA6000
EVA8000
EVA6000
MSCS on Windows
DataCenter 1 DataCenter 2
HP ContinuousAccess EVA
Cluster extension EVA for Windows
• What does it do?– Provides manual or automated site-
failover for Server and Storage resources
• Supported environments:– Microsoft Windows 2003 Enterprise
Edition (32-bit & 64-bit)– Microsoft Windows 2003 Data Center
Server(64-bit)– NAS4000 & 9000– HP Proliant DL380/580 Storage Server – Microsoft Cluster Service 5.2– Up to 500km
• Requirements:– EVA Disk Arrays– Cluster Extension EVA– Continuous Access EVA– Max 20ms network round-trip delay– Command View EVA & SMI-S
Cluster Extension EVA
Up to 500km
Windows 2003 stretched cluster with CA – Majority Node Set (MNS)
Continuous Access EVA
App A
App BQuorum Quoru
m
Quorum
App A
App B
• CA Failover• Restart Servers(Rescan)DRG A
DRG B
Cluster extension EVA: – Manual move of App A
DRG A
DRG BContinuous Access
EVA
App A
App BQuorum Quoru
m
Quorum
App A
• Move App A
Cluster extension EVA:- Storage failure
DRG A
DRG BContinuous Access
EVA
App A
App BQuorum Quoru
m
Quorum
App A
App B
Questions ?
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