Continuous Access
Overview
Damian McNamara
Consultant
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 location
Host writes its data to a LUN
Database
Mirror
Database
Continuous Access (3)
Source controller writes data in its cache
CA EVA copies data to remote controllers cache
Database
Mirror
Database
Continuous Access (4)
Remote controller sends ACK to local controller
Remote 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
Remote copying
• What does it do?
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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
Dest
VOL
Source
VOL
Source
VOL
Dest
VOL
DR groups and managed sets
DR Group
•
Consistent Group of replicated copy sets
(Vdisks)
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•
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
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Write Mode ([Synchronous] / Asynchronous)
Failsafe Mode (Enabled or [Disabled])
Suspend Mode ([Resume] / Suspend)
Failover command
Managed Sets
•
Another level of CA management
–
–
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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
EVA3000
EVA6000
EVA4000
• Fan-out of multiple relationships
– The ability for different LUNs on
one EVA to replicate to different
destination EVA
• Bidirectional
EVA5000
EVA8000
– one array with copy sets acting
as the source and destination
across the same intersite links
or fabric
EVA6000
EVA5000
EVA8000
Cluster extension EVA for Windows
•
What does it do?
– Provides manual or automated sitefailover for Server and Storage
resources
•
MSCS on Windows
– 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
Cluster Extension EVA
HP Continuous
Access EVA
•
DataCenter 1
DataCenter 2
Up to 500km
Supported environments:
Requirements:
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EVA Disk Arrays
Cluster Extension EVA
Continuous Access EVA
Max 20ms network round-trip delay
Command View EVA & SMI-S
Windows 2003 stretched cluster
with CA – Majority Node Set (MNS)
App A
App A
App B
App B
Quorum
Quorum
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•
DRG A
DRG B
CA Failover
Restart
Servers
(Rescan)
Continuous Access EVA
Quorum
Cluster extension EVA: –
Manual move of App A
App A
App A
App B
Quorum
Quorum
•
Move App A
DRG A
DRG B
Continuous Access EVA
Quorum
Cluster extension EVA:-
Storage failure
App A
App A
App B
App B
Quorum
Quorum
DRG A
DRG B
Continuous Access EVA
Quorum
Questions ?
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