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© 2009 IBM Corporation
IBM System Storage
IBM Software IBM Services
IBM Systems
Introduction to Selling Rapid Recovery Technology & Business Solutions
John SingExecutive IT Consultant WW System Storage singj@us.ibm.com
2© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
John Sing 27 years of experience with IBM in high end servers, storage, and software
► 2002-2009: IBM Systems Group Executive IT Consultant – IT and Business Continuity Strategy and Planning
► 1998-2001: IBM Storage Subsystems Group - Enterprise Storage Server Marketing Manager, Planner for ESS Copy Services (FlashCopy, PPRC, XRC, Metro Mirror, Global Mirror)
► 1994-1998: IBM Hong Kong, IBM China Marketing Specialist for High-End Storage
► 1989-1994: IBM USA Systems Center Specialist for High-End S/390 processors
► 1982-1989: IBM USA Marketing Specialist for S/370, S/390 customers (including VSE and VSE/ESA)
singj@us.ibm.com
© 2009 IBM Corporation
IBM System Storage
IBM Software IBM Services
IBM Systems
Introduction to IBM DS8000 Metro Mirror Consistency Group
4© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Concepts of Disk Mirroring
Copy data / logical LUN / file to a remote disk system ► Basically transferring a cache image to remote disk system
Important feature is Suspend / Resume
► When mirroring is suspended:● Disk subsystem uses bitmaps to track incremental changes during suspend
► Upon resync, only incremental changes need to be sent
Highly, highly recommended is a ‘tertiary’ copy (third copy)► Used for testing the restart, while keeping mirroring running
► Used for saving a golden’ copy
● In case of failure during resync● In case of problems during recovery / restart
5© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Synchronous Disk Mirroring What is synchronous disk
mirroring used for?► For applications that need zero data loss,
► Provides the tightest Recovery Point Objective
► BC Tier 6 or BC Tier 7 solution
Can be to a:► Remote location : for Disaster recovery with
zero data loss OR
► Local high availability: for local resiliency of storage in the local data center
Highly recommended to:► Have enough remote site disk to make ‘safety
copy’ (FlashCopy) of secondary disk - called “tertiary copy”
► In case of failure during resync
► To preserve a ‘golden’ copy, in case of problems during recovery / restart
SAN SAN
1. Application sends a write request1. Application sends a write request
3. Receipt confirmation from remote disk system
3. Receipt confirmation from remote disk system
2. Data written to remote disk cache2. Data written to remote disk cache
4. Write complete signal to the application4. Write complete signal to the application
Remote disk is exactly in “lock step”at the write I/O level
6© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Different ways to implement storage replication
In storage subsystem itself
In a storage
appliance
or
or
7© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Additional ways to use storage replication - 1
Point-in-Time followed by remote mirror
A
B
C
D
Point-in-Time followed by remote mirror followed by Point-in-Time
8© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Additional ways to use storage replication - 2
A C
B
A C
D
Point-in-Time from a remote mirror primary
Make a Point-in-Time safety copy of remote mirror
9© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Additional Ways to use replication - 3
A C
G
Sync mirroring for local / metro high availability
Async mirroring for Out of region recovery
10© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
IBM Disk Mirroring Technologies
DS8000
DS6000
ESS
DS5000DS3000 DS4000
N3000
.
N6000N7000
Entry
Midrange NAS/iSCSI Enterprise
SVC
Virtualization
Metro / Global MirrorThree site synchronous and asynchronous mirroring
► DS8000, N series
Global Mirror Asynchronous Mirroring DS8000, DS6000, ESS,
SVC, DS4000 / DS5000, N series
Metro Mirror Synchronous Mirroring DS8000, DS6000, ESS, SVC, XIV, DS4000 / DS5000, N series
XIV
11© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
What is Data Consistency
12© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Proper sequence of writes - for data consistency at application level
Many examples where start of one write operation is time dependent on the completion of a previous write
► Can be on a different disk group or even different disk frame► Database logs, catalogs, VTOCs, index & data components
Note that storage hardware by itself is just replicating the storage bit pattern► By itself, storage does NOT know about application inter-LUN, inter-volume dependencies
1. Log update
2. Updatedatabase
3. Mark Log - Update complete
13© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
i.e. do we wish to stop production, due to telecom line failure?
Usually, No. We wantproduction to keep running
If so, then what mayhappen is…..
Many application-level issues in disk mirroring This is just one example…..
In this example …. on a permanent link failure, disk mirroring simply marked the link as down, and accepted the I/O, in order to keep primary site production running ► i.e. do not want to stop production just because telecom went down
► As a result, #3 “Log Update Complete” flowed to remote.
Storage mirroring, by itself, doesn’t know about application-level, inter-LUN dependencies.
1. Log update
XPermanent
LinkFailure
3. Mark Log - Update complete
What Action?
Does remote
database match?
No! (bad!!)
14© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Wake Up Question“Synchronous disk mirroring all by itself, assures no application
data loss, and assures application restart.”True or False?
False
15© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
By itself, storage does not know about:► The inter-volume, application-level relationships
Therefore, when mirroring databases:► The concept of a session needs to be added to the disk mirroring functionality
This session is called a Consistency Group (CG)► Consistency Group session defines all of the volumes in the database
► Storage Consistency Group function manages and keeps data consistency across all of these volumes
Storage microcode (sometimes in combination with external server software) implements the Consistency Group function ► Possible to have CG span disk subsystems
● Using appropriate microcode or software
Data Consistency is provided by a Consistency Group function
16© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Global Mirror and Consistency Groups
Source Target
Data consistent copy
Across multiple LUNsConsistency Group
Method to maintain Consistency differs between sync and async mirroring
Asynchronous – CG creation and maintenance can be accomplished by different methods including:
►Point in Time identify at primary site and transmit changes;
►Time-stamping, Sequence numbers and sorting
►FIFO queue
17© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Consistency Group technology is different – many methods. The most commonly mis-understood is synchronous mirroring:
► We will show how DS8000 uses the concept of FREEZE
► FREEZE will suspend writing data to secondary, consistently, across all volumes in the Consistency Group
► Automation on a server is needed to monitor and manage synchronous mirroring Consistency Groups and FREEZE
► Understanding this allows one to more easily understand other storage replication Consistency Group mechanisms
Metro Mirror and Consistency Groups
REMEMBER : The goal is to create a consistent Point in Time copy at the secondary site that is recoverable.
18© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
DS8000 Metro Mirror Consistency Group FREEZE - 1
Upon error, top priority message gets sent to automation server
Automation server responds by sending FREEZE/SUSPEND command to all disk logical subsystems (LSSs)
Mirrored volumes in LSSs all go into “Extended Long Busy” – to assure that any and all write IO’s are queued across all volumes in Consistency Group
1. Log update
X
Automationserver
Action?
19© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
DS8000 Metro Mirror Consistency Group FREEZE - 2
Production continues to run, but incoming write I/Os are queued long enough so that automation server can…
SUSPEND all the mirroring links, across all LSSs and volumes in the CG
1. Log update
Automationserver
20© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
DS8000 Metro Mirror Consistency Group FREEZE - 3
Once FREEZE/SUSPEND is reported complete…
Automation server will issue FREEZE/RUN command, releasing all the queued IO to run locally. Production runs. If just a link failure, no outage to production.
1. Log update
Automationserver
However, as the mirroring links are suspended, the remote site received no further IOs, and is an exact Point in Time image as of the last instant before the error trigger event
21© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Consistency Group Consistency Group is a requirement for:► Any disk mirroring of multi-LUN, multi-
volume databases
Therefore, a disk platform selection consideration is:
► Always ask the customer what the maximum number of LUNs will be required to be in the same Consistency Group
► Various disk subsystems might have limits on maximum number of LUNs in a Consistency Group
● If more LUNs are required in a Consistency Group, you need to upgrade to a higher function storage subsystem
Source Volumes
Consistent secondaryvolumes
Database
Database Logs and Journals match
Data Tables
L
J
D
D
D
D
LD
DDD
JMirroring
L = Log J = Journal D = Data
22© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
Consistency Group Scalability and General Hierarchy
Metro Mirror Consistency Group
DS 3000► No native support (3400 via SVC)
DS5000/4000► Note: Does not support Metro Mirror Consistency
Group
XIV► Will support CG in YE2009, doesn’t support today
N series► Equivalent function provided by N series software
SAN Volume Controller► Maximum CG: 1,024 LUNs► Up to 256 consistency groups, 256TB target and
source capacity
DS8000, DS6000, ESS 800► Has largest and most scaleable Metro Mirroring► Maximum CG: Unlimited ► Multiple disk subsystems (or LSS’s) requires
automation software
Global Mirror Consistency Group
DS 3000► No native support (3400 via SVC)
DS5000/4000► DS5000 Global Mirror supports up to 128 LUNs in
a Consistency Group
XIV► Available YE2009, doesn’t support today
N Series► Equivalent function provided by N series software
SAN Volume Controller (at SVC 5.1)► Maximums CG: 1024 LUNs► Up to 256 consistency groups, 256TB target and
source capacity
DS8000, DS6000, ESS 800► Largest and most scaleable Global Mirroring► Maximum CG: Up to 17 primary side DS8000
systems ► Supports any attaching platforms (can be mix of
platforms )
23© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems 23
Learning Points
The concept of Consistency Groups can be explained as follows:
By itself, storage does not know about:
► The inter-volume, application-level relationships
Therefore, when mirroring databases:
► The concept of a session needs to be added to the disk mirroring functionality.
This session is called a Consistency Group
► Consistency Group session defines all of the volumes in the database
► Consistency Group function manages and keeps data consistency across all of these volumes
Storage microcode (sometimes in combination with external server software) implements the Consistency Group function
24© 2009 IBM Corporation
Storage Sales Academy
IBM Software IBM Services IBM Systems
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