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Transcript of Copyright © 2014 EMC Corporation. All Rights Reserved. SnapView Snapshot Upon completion of this...
Copyright © 2014 EMC Corporation. All Rights Reserved.
SnapView Snapshot
Upon completion of this module, you should be able to:• Describe SnapView Snapshot operations• Configure and Manage SnapView Snapshots
SnapView Snapshot 1
Copyright © 2014 EMC Corporation. All Rights Reserved.
SnapView Snapshots
During this lesson the following topics are covered: • Purpose of SnapView Snapshot• SnapView Snapshots requirements• SnapView Snapshots managed objects• SnapView Snapshots theory of operations
Lesson 1: Theory and Operation
SnapView Snapshot 2
Copyright © 2014 EMC Corporation. All Rights Reserved.
SnapView Snapshots
• SnapView Snapshot - an instantaneous frozen virtual copy of a LUN on a storage system Allows a secondary server to view a point-in-time copy of a source
LUN Snapshots are created instantly – no data is copied at creation time Snapshot will not change UNLESS the user writes to it Original view available by deactivating changed Snapshot
• Virtual LUN Not a real LUN - made up of pointers, original and saved blocks Uses a copy on first write (COFW) mechanism Requires a ‘save area’ – the Reserved LUN Pool
SnapView Snapshot 3
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SnapView Snapshots Requirements
Environment System Requirements
Hardware VNX Storage SystemTwo or more Servers (if the SnapView snapshot is to be accessed by a host), each attached to the VNX that will run SnapView
Storage System Software VNX Operating Environment for BlockSnapView enabler
Management Software Unisphere UINavisphere Secure CLIAdmsnap
Operating Systems HP-UXIBM AIXLinuxSolarisWindows Server
Refer to EMC Support Matrix for a complete list
SnapView Snapshot 4
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SnapView Snapshots Managed Objects
• Source LUN The LUN containing production data
• SnapView Session Process of defining the point-in-time designation Invokes COFW activity for updates to the source LUN
• Reserved LUN Supports the pointer-based design of SnapView Snapshot Used to save data chunks
• SnapView Snapshot The defined virtual LUN Presented to the secondary host Enables visibility into running sessions
SnapView Snapshot 5
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SnapView Session
• SnapView Session COFW mechanism starts and ends with session SnapView snapshot appears off-line until there is an active session A multiple Source LUN session can be started consistently
• SnapView Session name Sessions should have significant names Compatibility with admsnap – use alphanumerics, underscores It’s case-sensitive!
• Session consistent start Holds I/O until session starts on all source LUNs Fails if any source LUN fails Does not allow other LUNs to be added to session
SnapView Snapshot 6
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Copy on First Write
• Allows efficient utilization of copy space Uses a dedicated save area – the Reserved LUN Pool Total capacity of Reserved LUN Pool LUNs is approximately 20% of
total source LUN sizes
• Saves original data chunks – once only Chunks are a fixed size - 64 KB (128 blocks) Chunks are saved when they’re modified for the first time
• Allows consistent ‘point-in-time’ views of LUN(s)• Allows rollback to previous points in time
SnapView Snapshot 7
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Reserved LUN Recommendations
• Total number of Reserved LUNs is VNX model-dependent• Reserved LUNs may be of different sizes• No checking of size, disk type or RAID type when allocated• Use SAS drives with write-cache enabled LUNs• Thin LUNS cannot be used in the RLP• Create 2 RLs per Source LUN, each 10% of Source LUN size• Example
LUNs to be snapped: 10 GB, 20 GB, 30 GB, 100 GB Average LUN size = 160 GB/4 = 40 GB Make each Reserved LUN 4 GB in size Make 8 Reserved LUNs
SnapView Snapshot 8
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SnapView: Stopping Sessions
• Sessions may be manually stopped by the user • SnapView Sessions are automatically stopped
If the Reserved LUN Pool fills (attempt to use too much disk space)
• Stopping the SnapView Session Removes all memory map entries associated with session Reserved LUN Pool space is made available for reuse
SnapView Snapshot 9
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Host I/O to a Source LUN
• Three possible types of I/O to a source LUN1. Read or write request with no active session
I/O passed to driver below in I/O stack2. Read request with active session
I/O passed to driver below in I/O stack3. Write request with an active session
If the original data is not already in the Reserved LUN Pool, Copy on First Write is performed Original data read from source LUN SnapView finds an unused area in the Reserved LUN Pool Original data written to unused area in Reserved LUN Pool Entry made in memory and on disk to indicate where original data is
written Write request passed to driver below in I/O stack
If the original data is already in the Reserved LUN Pool, the write request is passed to driver below in I/O stack
SnapView Snapshot 10
Copyright © 2014 EMC Corporation. All Rights Reserved.
Host I/O to a Snapshot
• Three possible types of I/O to a Snapshot1. Read or write request with no active session is intercepted by
the SnapView driver I/O requests fail – drive appears off-line
2. Read request with an active session Memory map consulted to determine if the data should be read
from the Reserved LUN Pool or from the source LUN3. Write request with an active session
Write requests are allowed; however, any data written to a Snapshot is not persistent beyond the end of the session
The memory map is consulted to determine if the original data has been written to the Reserved LUN Pool (i.e., COFW has already occurred)
If not, a new map entry is created, and the original data is written to the RLP. The new data is written to the Source LUN
SnapView Snapshot 11
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SnapView Snapshot Theory of Operation
SnapView Snapshot 12
8AM 9AM
ProductionServer
A B C
SourceLUN
Chunks
A B CChunks
Session 9AM
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
SourceLUN
ContinuousI/O
1 Session 9AM is started
Reserved LUN 6 is allocated
COFW is enabled
1
1
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 13
10AM
A B C
Source LUN
Chunks
Session 9AM
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
A B CChunks
Snapshot ofSource LUN
2 Snapshot of Source LUN is createdbut not activated2
Server BSnapshot of Source LUN is addedto the Storage Group of Server B
3
3Not Ready
ProductionServer
R / W
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 14
A B C
Source LUN
Chunks
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
4 Snapshot of Source LUN is activated
4
Snapshot ofSource LUN
A B CChunks
Session 9AM
Session 9AM is allocated by Snapshotof Source LUN
Server B
ProductionServer
11AM
R / W
R / W
Virtual Source LUN (Snapshot of Source LUN)is made available (R / W) to Server BA B C
Chunks
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 15
A B C
Source LUN
Chunks
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
5 Production Server requests a changeon Chunk “C” (COFW)
5
Snapshot ofSource LUN
A B CChunks
Session 9AM
Server B
ProductionServer
12PM
R / W
R / W
C’
6C
6Original Chunk “C” is copied to theReserved LUN 6 allocated by Session 9AM
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 16
A B C’
Source LUN
Chunks
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
7 Session 9AM pointer uses the originalChunk ‘C” from Reserved LUN 6
Snapshot ofSource LUN
A B CChunks
Session 9AM
Server B
ProductionServer
12PM
R / W
R / W
7
C
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 17
A B C’
Source LUN
Chunks
LUN 6 LUN 7
LUN 8 LUN 9
Reserved LUN Pool
8
Snapshot ofSource LUN
A B CChunks
Session 9AM
Server B
ProductionServer
1PM
R / W
R / W
8
C
B’
Server B requests a change on Chunk “B” (COFW)
B
9
9
Original Chunk “B” is copied to theReserved LUN 6 allocated by Session 9AMand then modified by the write
B’
’
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SnapView Snapshot Theory of Operation (continued)
SnapView Snapshot 18
A B C’
Source LUN
Chunks
LUN 6LUN 7
LUN 8 LUN 9
Reserved LUN Pool
Snapshot ofSource LUN
A B’ CChunks
Server B
ProductionServer
1PM
R / W
R / W CB’
Session 9AM
Session 9AM pointer usesChunk B’ from Reserved LUN 6
01
01
B
Copyright © 2014 EMC Corporation. All Rights Reserved.
SnapView Snapshots
During this lesson the following topics were covered:• Purpose of SnapView Snapshot• SnapView Snapshots requirements• SnapView Snapshots managed objects• SnapView Snapshots theory of operations
Lesson 1: Summary
SnapView Snapshot 19
Copyright © 2014 EMC Corporation. All Rights Reserved.
SnapView Snapshots
During this lesson the following topics are covered: • Managing the Reserved LUN Pool• Managing SnapView sessions and SnapView snapshots • Configuring and managing SnapView sessions and SnapView
snapshots with the Wizards
Lesson 2: Configuring and Managing SnapView Snapshots
SnapView Snapshot 20
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Reserved LUN Pool Management
21SnapView Snapshot
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Reserved LUN Pool LUNs – Free LUNs
22SnapView Snapshot
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Reserved LUN Pool – Allocated LUNs
23SnapView Snapshot
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Monitoring Reserved LUN Pool Usage
Storage System > System > Monitoring and Alerts > SP Event Logs
24SnapView Snapshot
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SnapView Sessions
25SnapView Snapshot
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SnapView Session Properties
Storage System > Data Protection > Snapshots > LUN Snapshots
26SnapView Snapshot
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SnapView Session – Start / Stop
27SnapView Snapshot
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SnapView Snapshot
28SnapView Snapshot
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Snapshot Session Rollback
29SnapView Snapshot
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Snapshot Session Rollback Properties
30SnapView Snapshot
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Snapshot Configuration Wizard
31SnapView Snapshot
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SnapView Snapshots
During this lesson the following topics were covered:• Managing SnapView snapshots and SnapView sessions• Configuring and managing SnapView snapshots and sessions
with the Snapshot Wizard
Lesson 2: Summary
32SnapView Snapshot
Copyright © 2014 EMC Corporation. All Rights Reserved.
Summary
Key points covered in this module:• SnapView Snapshot is an instantaneous frozen virtual copy of a
LUN on a VNX storage system• SnapView Snapshot uses COFW technology• Snapshot Wizard can be used to Configuring and managing
SnapView snapshots and sessions
SnapView Snapshot 33