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Page 1Technology Spotlight Seminar - SRDF
Technology Spotlight on
EMC Symmetrix
Remote Data Facility
Technology Spotlight on
EMC Symmetrix
Remote Data Facility
Page 2Technology Spotlight Seminar - SRDF
Agenda
Enterprise Storage
SRDF Introduction
Business Challenges
SRDF Configurations
SRDF Operational Modes
SRDF Operation
Page 3Technology Spotlight Seminar - SRDF
Enterprise Storage Framework
InformationProtection
InformationSharing
InformationManagement
SDMSESP SMTF DataReachTM SNFS
Symmetrix
Manager
FDRSOS EDM
Internet
Services
InformationProtection
InformationSharing
InformationManagement
SDMSESP SMTF DataReachTM SNFS
Symmetrix
Manager
FDRSOS EDMTime
FinderTM
TimeFinderTM
Internet
Services
ENTERPRISE STORAGE
TimeFinderTMSRDF
Page 4Technology Spotlight Seminar - SRDF
SRDF IntroductionSRDF Introduction
Page 5Technology Spotlight Seminar - SRDF
What Does SRDF Do?
SRDF creates and maintains real time or near real time physically separate copy of data, without using host cycles, in a local or remote EMC Symmetrix that can be directly addressed by a designated Host system even in the event of individual drive or link failures.
Page 6Technology Spotlight Seminar - SRDF
SRDF Nomenclature
Local Volume— May be spared, locally mirrored,
unmirrored or part of a RAID-S group
Source Volume— An active application volume containing
production data and programs. The Standard Volume may be locally mirrored, unmirrored, part of a RAID-S group, and/or covered by a global spare.
Target Volume— A volume that contains the copy of a
Source Volume
Synchronized Volumes— The background task performed by
Symmetrix to create an identical mirror image of two volumes; as in RAID 1One volume is always Synchronized to another.
RLD, Remote Link Director— Symmetrix SRDF Communication feature
Configuration Types— Unidirectional — Bi-directional— Uni-directional
Primary Operational Modes— Synchronous— Semi-synchronous
Secondary Operational Modes— Adaptive Copy— Domino— Invalid Tracks
Other Definitions— M1: A Source Volume— M2: The RAID 1 mirror of the
M1— R1: Source side of Remote
Mirror— R2: Target side of Remote
Mirror
Page 7Technology Spotlight Seminar - SRDF
Symmetrix Remote Data Facility
Extended Distance(T1/T3, E1/E3, ATM)
Campus (66Km)
Logically synchronized versions of selected volumes
Independent of CPU, operating system, application or database
Resilient against drive, link and server failures Selectable synchronization behavior
Page 8Technology Spotlight Seminar - SRDF
Business ChallengesBusiness Challenges
Page 9Technology Spotlight Seminar - SRDF
The Business Challenge
The Business Problem—Data inaccessibility measured in $$$$—Continuous availability for all data becoming the norm —Disaster recovery for business receiving renewed
focus
Symmetrix Remote Data Facility—Maintain real-time or near-real-time physically
separate copy of selected volumes—Use no host CPU resources—Operating system independent—Continue running through events such as individual
drive/link failures
Page 10Technology Spotlight Seminar - SRDF
SRDF Applications
Business Continuance—Act as separate mirror for business and application
continuance
Disaster Recovery —Very rapid data availability with data current to last
write
Data Center Migration—Effect data center move with minimum application
outage
Workload Management—Provide service through scheduled outages such as
maintenance
Page 11Technology Spotlight Seminar - SRDF
Disaster Recovery with SRDF
Disaster recovery across the enterprise —Consolidates heterogeneous platforms into one DR
solution
Restart applications at recovery site with no data restore required —Maximized application availability
Test Disaster Recovery process in place—Validate completeness of DR plan to minimize
“surprises”
Return home after disaster recovery with minor disruption—Synch and re-synch automated and transparent to users
Page 12Technology Spotlight Seminar - SRDF
SRDF ConfigurationsSRDF Configurations
Page 13Technology Spotlight Seminar - SRDF
SRDF Uni-Directional Configuration
SITE BSITE A
CPU(s) OptionalCPU(s)
LocalLocal SourceSource TargetTargetLocalLocal
Fibre, ATM, or T1/T3
RLD 1RLD 1RLD 1RLD 1
RLD 2RLD 2RLD 2RLD 2
Active Path
Recovery Path
... ...
Page 14Technology Spotlight Seminar - SRDF
SRDF Bi-Directional Configuration
SITE BSITE A
CPU(s) CPU(s)
LocalLocal SourceSource TargetTargetLocalLocal
Fibre Only
RLD 1RLD 1RLD 1RLD 1
RLD 2RLD 2RLD 2RLD 2
Active Path
Recovery Path
...
TargetTarget SourceSource
...
Page 15Technology Spotlight Seminar - SRDF
Dual SRDF Configuration
SITE BSITE A
CPU(s) CPU(s)
LocalLocal SourceSource TargetTargetLocalLocal
Fibre, ATM, or T1/T3
RLD 1RLD 1 RLD 1RLD 1 RLD 1RLD 1RLD 1RLD 1
Active Path
Recovery Path
...
TargetTarget SourceSource
...
RLD 2RLD 2 RLD 2RLD 2 RLD 2RLD 2RLD 2RLD 2
Page 16Technology Spotlight Seminar - SRDF
Campus Solution
Active ChannelPrivate or Common Carrier - 46-66 km max, Repeater required every 20-30 kmRecovery ChannelRecovery Channel
Private Fiber or Common Carrier
9036903290339191
9036903290339191SITE A SITE B
Page 17Technology Spotlight Seminar - SRDF
Extended Distance Solution
Active ChannelLeased Carrier - Distance Limited to CarrierRecovery ChannelRecovery Channel
ATM, T3 or E3
SITE A SITE B
OtherNetworkDevice
OtherNetworkDevice
Page 18Technology Spotlight Seminar - SRDF
Extended Distance: The Problem
Speed of light (186,000 miles/sec) is Constant!
1ms delay per 125 miles ( x 2 for response)—8ms for send and confirm across a 500 mile trek
Single Queue, Multiple Servers (RLDs).
For a 500 mile link - I/O from 6 devices queued—first 2 devices delayed 8ms each—next 2 delayed ~ 16ms each— last 2 delayed ~ 24ms each— links are idle 87% of the time - more for longer
distances
Page 19Technology Spotlight Seminar - SRDF
Extended Distance: Standard and FarPoint
Dev 0
Dev 4Dev 3Dev 2Dev 1
RLD
Queue
Dev 0
Dev 4Dev 3Dev 2Dev 1
Queue
SRDF FarPointSRDF FarPoint
RLD RLDDATA & Cmd
STATUS
SRDF Standard ModeSRDF Standard Mode One block per link. Link waits for confirming response.
Multiple Logical Devices per link. Device waits for confirming
Response.
RLD
Page 20Technology Spotlight Seminar - SRDF
Extended Distance: FarPoint
Send Multiple -- Confirm Multiple
Multiple devices, multiple servers (RLDs)
Queued in order received
Up to n transactions in the “Pipe” at any time—Variable Based on Bandwidth, Distance,
and Block size
Page 21Technology Spotlight Seminar - SRDF
FarPoint: Impact
Higher Level of Throughput
Leveling of Response Time
Base Response Times Not Changed—Speed of Light Unaffected.
More Impact at Higher Distances and Heavier Loads
Page 22Technology Spotlight Seminar - SRDF
FarPoint: Special Considerations
Requires 5x64 microcode—Default for Extended Distance (T3/E3)
Supported—Synchronous mode—Semi Synchronous Mode—Adaptive Copy Mode
Not Supported—Bi-Directional Mode
Error Recovery—Flush the Pipe—Revert to Standard Mode
Page 23Technology Spotlight Seminar - SRDF
SRDF Operational ModesSRDF Operational Modes
Page 24Technology Spotlight Seminar - SRDF
SRDF Modes of Operation
Synchronous
Semi-Synchronous
Adaptive Copy—Disk Mode—Write Pending Mode
SRDF Processes I/O to RemoteSRDF Processes I/O to RemoteSymmetrix in Serialized QueuesSymmetrix in Serialized Queues
SRDF Updates I/O to RemoteSRDF Updates I/O to RemoteSymmetrix PeriodicallySymmetrix Periodically
Based on Time Slice SettingBased on Time Slice Setting
Page 25Technology Spotlight Seminar - SRDF
From SCSI Adapters, ESCON Adapters,
Fibre Adapters or Channel Adapters
To RLD’s
SRDF Serialized Queue
Volume 16
Volume 21
Volume 5
Volume 62
Volume 3
Volume 10
Queue of Updates from Source Symmetrix to Remote Symmetrix
FIFO Queue : First-In-First-Out
Maximum of one I/O per Volume in the Queue at any Time
Page 26Technology Spotlight Seminar - SRDF
SRDF Synchronous Mode
SourceSourceLocalLocal
1. Local Symmetri
x receives
a write from
the Host
2. Local Symmetrixtransmits data to theRemote Symmetrix
3. Receiptacknowledgedby RemoteSymmetrix
4. Ending statuspresented to Host
TargetTargetLocalLocal
Page 27Technology Spotlight Seminar - SRDF
SRDF Synchronous Mode
Data integrity of all copies is maintained
Local and Remote Symmetrix maintain a synchronized copy of data
I/O is Serialized and placed on Symmetrix System Wide FIFO Queue
“I/O Elongation” - Duration of time for each I/O is increased due to serial activity PRIORITIESPRIORITIES
Data IntegrityDisaster Recovery
Source TargetSource TargetSource Data Always Equals Target Data
Page 28Technology Spotlight Seminar - SRDF
SRDF Semi-Synchronous Mode
SourceSourceLocalLocal
1. Local Symmetri
x receives
a write from
the Host
3. Local Symmetrixtransmits data to theRemote Symmetrix
4. Receiptacknowledgedby RemoteSymmetrix
2. Ending statuspresented to Host
TargetTargetLocalLocal
Page 29Technology Spotlight Seminar - SRDF
SRDF Semi-Synchronous Mode
I/O to Remote Symmetrix is done in parallel—Reads are executed even while
writes are in transit to Remote Symmetrix
—Additional writes wait until original write is acknowledged
Local and Remote Symmetrix maintain a nearly synchronized copy of data
I/O is Serialized and placed on Symmetrix System Wide FIFO Queue
“I/O Elongation” is eliminated
PRIORITIESPRIORITIESPerformanceData IntegrityDisaster Recovery
Source TargetSource TargetSource Data Almost Equals Target Data
Out of Synch by 1 I/O per Volume at most
~~~~
Page 30Technology Spotlight Seminar - SRDF
SRDF Adaptive Copy Mode
SourceSourceLocalLocal
1. Local Symmetrix
receives writes from
the Host
4. Local Symmetrixtransmits data flaggedas updated based onTime Slice to theRemote Symmetrix
5. Receiptacknowledgedby RemoteSymmetrix
2. Ending statuspresented to Host
TargetTargetLocalLocal
3. SRDF Flags the Recordfor later Update to Remote
Page 31Technology Spotlight Seminar - SRDF
From SCSI Adapters, ESCON Adapters,
Fibre Adapters or Channel Adapters
a
To RLD’s
SRDF Queue of Adaptive Copy Updates
Updates are Time Sliced into Queue
Default Setting is 1 in 10—Every Tenth I/O is
an Update to the Remote Symmetrix
Setting can be changed at any time
Volume 16Volume 5
Volume 19Volume 3
Volume 10Volume 13Volume 14Volume 7Volume 8
Time Slice UpdateVolume 17
Page 32Technology Spotlight Seminar - SRDF
SRDF Adaptive Copy Mode
I/O to Remote Symmetrix is done in parallel— Reads and Writes are executed
even while updates are pending or in transit to Remote Symmetrix
— No Serialization of I/O data to Remote Symmetrix by Arrival Sequence
— Host I/O placed on FIFO Queue periodically as determined by AD-COPY RATE
Data movement occurs with minimal impact on Local Host and Local Symmetrix
Adaptive Copy Configurations— Disk Mode— Write Pending Mode
PRIORITIESPRIORITIESMoving DataOn Line Backup at Remote Site
Source TargetSource TargetSource Data does not Equals Target Data
Possibly Out of Synch by ‘N’ tracksbased on Symmetrix Activity
Page 33Technology Spotlight Seminar - SRDF
SourceSourceLocalLocal
SRDF Domino
TargetTargetLocalLocal
Domino Configuration Sets Volumes to NOT READY State if Any One of the Following Occurs:—Source Unavailable—Links Unavailable—Target Unavailable
Links Only Option Sets Volumes to NOT READY Only if Links are Unavailable
Source Target
Links
Page 34Technology Spotlight Seminar - SRDF
SourceSourceLocalLocal
SRDF Invalid Tracks
TargetTargetLocalLocal
Notification of Invalid Tracks Provided
Stops Target Volumes from Becoming Ready When Multiple Links Fail
Source Target
Links
Page 35Technology Spotlight Seminar - SRDF
SRDF OperationSRDF Operation
Page 36Technology Spotlight Seminar - SRDF
Error Reporting and Diagnostics
Message reporting to Host/Server console
Auto Call on abnormal conditions in HDA, link, subsystem
Remote support facility diagnostics
Page 37Technology Spotlight Seminar - SRDF
SourceSourceLocalLocal
Loss of Drive at Primary Site
TargetTargetLocalLocal
Source Target
Links
Primary Host Remote Host
PrimarySymmetrix
RemoteSymmetrix
Page 38Technology Spotlight Seminar - SRDF
Loss of Drive at Site A
Application continues to run on Host/Server at Site A
Read/Write operation on affected drive go to Target volume at Site B
Exposure if Target volume lost (no local mirroring)
MESSAGE: with address of failed device
Repair drive at Site A
Command to resync: from Target to Source
MESSAGE: when resync. starts
MESSAGE: when resync. complete
Page 39Technology Spotlight Seminar - SRDF
SourceSourceLocalLocal
Loss of Primary Site
TargetTargetLocalLocal
Source Target
Links
Primary Host Remote Host
PrimarySymmetrix
RemoteSymmetrix
Page 40Technology Spotlight Seminar - SRDF
Loss of Primary Site
Single command makes target drives accessible to recovery Host/Server CPU
Command can be issued from:—Service processor console—Remote support center—Local host using host component
Applications resumed within minutes at most recent status
Page 41Technology Spotlight Seminar - SRDF
SRDF Host Component
Runs as MVS subsystem
Optional, chargeable, licensed per CPU
Complements SRDF base system
Initiated via started task
Uses SAI to retrieve information from Symmetrix subsystem
Provides status and configuration control
Extends automated operations to contingency planning
Page 42Technology Spotlight Seminar - SRDF
ENTERPRISE STORAGE
MEDIA
PLATFORM-SPECIFIC CONTROLLERS
MAINFRAME OPEN NETWORK DATABASE
Enterprise Storage Checklist
Enterprise connectivity
Cascadable
Information-centric— Information
protection — Information sharing— Information
management
Business Impact
Operational Impact
Financial Impact
Business Impact
Operational Impact
Financial Impact