Page 1 Technology Spotlight Seminar - SRDF Technology Spotlight on EMC Symmetrix Remote Data...

Technology Spotlight Seminar - SRDF

Technology Spotlight on

EMC Symmetrix

Remote Data Facility

Technology Spotlight on

EMC Symmetrix

Remote Data Facility


Agenda

Enterprise Storage

SRDF Introduction

Business Challenges

SRDF Configurations

SRDF Operational Modes

SRDF Operation


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


SRDF IntroductionSRDF Introduction


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.


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


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


Business ChallengesBusiness Challenges


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


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


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


SRDF ConfigurationsSRDF Configurations


SRDF Uni-Directional Configuration

SITE BSITE A

CPU(s) OptionalCPU(s)

LocalLocal SourceSource TargetTargetLocalLocal

Fibre, ATM, or T1/T3

RLD 1RLD 1RLD 1RLD 1


Active Path

Recovery Path

... ...


SRDF Bi-Directional Configuration

SITE BSITE A

CPU(s) CPU(s)


Fibre Only



Active Path

Recovery Path

...

TargetTarget SourceSource

...


Dual SRDF Configuration

SITE BSITE A

CPU(s) CPU(s)


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


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


Extended Distance Solution

Active ChannelLeased Carrier - Distance Limited to CarrierRecovery ChannelRecovery Channel

ATM, T3 or E3

SITE A SITE B

OtherNetworkDevice

OtherNetworkDevice


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


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


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


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


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


SRDF Operational ModesSRDF Operational Modes


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


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


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


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


SRDF Semi-Synchronous Mode


1. Local Symmetri

x receives

a write from

the Host

3. Local Symmetrixtransmits data to theRemote Symmetrix





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

~~~~


SRDF Adaptive Copy Mode


1. Local Symmetrix

receives writes from

the Host

4. Local Symmetrixtransmits data flaggedas updated based onTime Slice to theRemote Symmetrix




3. SRDF Flags the Recordfor later Update to Remote


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


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



SRDF Domino


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



SRDF Invalid Tracks


Notification of Invalid Tracks Provided

Stops Target Volumes from Becoming Ready When Multiple Links Fail

Source Target

Links


SRDF OperationSRDF Operation


Error Reporting and Diagnostics

Message reporting to Host/Server console

Auto Call on abnormal conditions in HDA, link, subsystem

Remote support facility diagnostics



Loss of Drive at Primary Site


Source Target

Links

Primary Host Remote Host

PrimarySymmetrix

RemoteSymmetrix


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



Loss of Primary Site


Source Target

Links

Primary Host Remote Host

PrimarySymmetrix

RemoteSymmetrix


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


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


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

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