SnapView Clones
Upon completion of this module, you should be able to:
• Describe SnapView Clone operations
• Manage SnapView Clones
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SnapView Clones
Lesson 1: SnapView Clone: Theory and Operation
During this lesson the following topics are covered:
• Purpose of SnapView Clones
• SnapView Clones requirements
• SnapView Clones managed objects
• SnapView Clones theory of operations
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SnapView Clones
• SnapView Clone – a full copy of a LUN internal to a storage
•
system
Population latency
 Clones take time to populate (synchronize)
 Data in the LUN must be duplicated
• Protected
 No changes will be made to the clone UNLESS the user writes to it
• 2-way synchronization
 Clones may be incrementally updated from the source LUN
 Source LUNs may be incrementally updated from a clone
• Copies real data
 Clone must be EXACTLY the same size as Source LUN
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SnapView Clones Operations
• Create Clone Group
 Changes LUN to source LUN
• Add clone to Clone Group
 Changes LUN to clone
• Synchronize Clone
 Data copied from source LUN to clone
• Fracture clone (may be a consistent operation)
 Stops updating of clone with new source LUN data
• Remove clone
 Clone becomes an independent LUN
 Cannot be synchronizing or reverse synchronizing
• Destroy Clone Group
 Source LUN becomes an independent LUN
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Clone Initial Synchronization
• Copy contents of source LUN to clone
 Overwrites clone with source LUN data
 Host access allowed to source LUN at all times
 No host access to clone while not fractured
Production Host
Source
LUN
Backup Host
X
Clone 1
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Clone 2
...
Clone 8
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Clone Private LUN (CPL) and Fracture Log
• Fracture Log




Bitmap stored in SP memory
Tracks modified extents between source LUN and each clone
Allows incremental resynchronization – in either direction
Determines extent size
 1 block for each GB of source LUN size, with a minimum of 128 KB
 Example: 512 GB clone. Extent size = 512 blocks = 256 KB
• Private LUN for each SP





Must be 1 GB or greater
Used for all clones owned by the SP
No clone operations allowed until CPL created
Contains persistent Fracture Logs
Classic LUNS only
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Clone Reverse Synchronization
• Restore source LUN with contents of clone
 Overwrites source LUN with clone data
 Host access allowed to source LUN
 No host access to clone
 Source LUN instantly appears to contain clone data
Production Host
Source
LUN
X
Backup Host
X
X
Clone 1
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Clone 2
...
Clone 8
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Reverse Synchronization and Protected Restore
• Non-Protected Restore
 Host → source LUN writes mirrored to clone
 When Reverse Synchronization completes:
 Reverse-synchronized clone remains unfractured
 Other clones remain fractured
• Protected Restore
 Host → source LUN writes not mirrored to clone
 When Reverse Synchronization completes:
 All clones are fractured
 Protects against source LUN corruption
 Configure at the individual clone level
 Must be globally enabled first with ‘Allow Protected Restore”
checkbox
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Trespassing Source LUNs and Clones
• Source LUN Trespass
 Peer SP acquires clones
 Peer SP acquires Fracture Logs (through CPL)
 Peer SP resumes any synchronization operations
• Clone Trespass
 User or host can initiate trespass of a fractured clone
 Desirable for load balancing across SPs
 Fractured clone need not be on same SP as source LUN
 Synchronization trespasses clone as necessary
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SnapView Clones
Lesson 1: Summary
During this lesson the following topics were covered:
• Purpose of SnapView Clones
• SnapView Clones requirements
• SnapView Clones managed objects
• SnapView Clones theory of operations
Copyright © 2014 EMC Corporation. All Rights Reserved.
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SnapView Clones
Lesson 2: Clone Configuration
During this lesson the following topics are covered:
• Clone configuration
• Creating and populating Clone Groups
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Configuring the Clone Private LUNs
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Creating a Clone Group
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Adding a Clone to a Clone Group
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Clone Group Properties
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Clone Operations
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Clone Operations - Consistent Fracture
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Clone Time of Fracture
• Allows the user to know the date/time when the Clones images
•
•
•
•
were administratively fractured
Clones will stamp the time ONLY when the clones were
administrative fractured by the user and the images were a point
in time copy (consistent state)
The time will be stored persistently inside the current clones
private area in PSM
All Clones involved in a Consistent Fracture operation reports the
same time of fracture
Private LUN for each SP
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Clone Configuration Wizard
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SnapView Clones
Lesson 2: Summary
During this lesson the following topics were covered:
• Clone Private LUN configuration
• Clone operations
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Summary
Key points covered in this module:
• SnapView Clone is a full copy of a LUN internal to a VNX storage
system
• Clones take time to duplicate data from source
• Clones must be exactly the same size
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