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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