Comdex Brasil August 2004 Storage Presentation

COMDEX Brasil São PauloStorage Conference

19 August 2004 Afternoon 45 minutes

Choosing the Best Solutions for Business

Continuity

Tom FlesherE-Net Corporation

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Choosing the Best Solutions for Business Continuity

Session Abstract & Outline Abstract: Choosing the best solution for business continuity and log replication

– Data replication and high availability technologies are essential for business continuity. In this presentation, the speaker compares and contrasts options for data contingency and business continuity, including case studies. Outline

– Topic 1: Remote replication benefits Business Continuity Availability Load Balancing Special applications for replication

– Topic 2: Remote replication alternatives Hardware and software solutions Data Base Shadowing – uni-directional replication Peer-to-peer Replication Disk Mirroring Remote Vaulting & Journaling

– Topic 3: Cost comparison of the different solutions– Topic 4: Case studies

US Financial Services Industry US Securities Industry

– Topic 5: Discuss: Next step?

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Why replicate critical databases over extended distance?

Simple answer: “…to have a hot standby copy of your organization’s most critical data at a remote location in case you need it.” Your needs may include one or more of the following:

Business continuity Your primary copy of the data is knocked out or is unavailable for an

unacceptable length of time – in other words, an “unscheduled outage”

Continuous availability Your primary copy will be unavailable due to a planned and deliberate

event, such as maintenance, migrations or reorganizations

Workload balancing, data mining and replication You can run data mining applications against the replica copy and

avoid the overhead on the primary copy Replica copy can, with some solutions, be “paused” at a point of logical

consistency at any desired point in time

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Demands on Your Data

CALL CENTER

Production Database

EDI

OLTP

INTERNET

Analysis

Data Mining

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Benefits of Extended Distance Database Replication

Production Database

ReplicaDatabase

Business Continuity– Not compromised by

regional outage

Availability– Switch to backup site

during scheduled outages

Application-driven– Ad hoc queries– Warehousing– Data mining

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What’s the difference between mirroring and replication?

Mirroring is hardware-based replication…– All changed data is sent to the remote location at the physical track

level– Always homogeneous (identical) and uni-directional– Can be synchronous over relatively short distances

– Must be asynchronous over extended distance …but there’s also software-based replication

– Change data may be sent in the form of log/journal records, MQ messages, time-triggered “sweeps” of source

– May be heterogeneous (different) and bi-directional, star clustered or peer-to-peer

Mirroring is, by definition, a hardware-based solution Replication may be accomplished using hardware and/or

software facilities

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Using mirrored disks for hardware-based replication

Mirroring assumes a “system restart” at takeover time – All database files, logs, catalogs must be mirrored faithfully– Notion of “time-consistent restart state” – simulation of the

local/production site environment at a precise point in time– Enables database management systems to perform warm restart

process – backout of inflight transactions (ACID) and cleanup of dirty pages (e.g. Aries/DB2) - to restore database to a consistent state

– After warm restart, data is ready to be used for application takeover Point-in-time copies can be spun off when needed

– For recovery testing– To support read-only applications– To freeze the entire environment while a new full copy is being

transmitted

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Refresh vs. Change Propagation

A Refresh involves a full copy of all data– Time-consuming – Needs lots of bandwidth– Required for all replication solutions

Some permit tape / CTAM refresh…..

– Potential impact on production application

Change propagation involves capture and transmission of changes– Physical (track) vs. logical (record)

Bandwidth considerations

– Synchronous and asynchronous components

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Track/Page vs Record/Row

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Challenges over Extended Distance

Propagation Delay– A fully asynchronous solution should have adequate buffering and

recovery capabilities to run over any distance– Satellite links have huge propagation delays, yet typically very high

bandwidth! Bandwidth

– How many bits must move across the network over time?– Include refresh in addition to change propagation requirements

Time to re-sync in event of extended network outage– Just changed data or all data?

Cost– Pure hardware cost, count extra copies!– Recurring network costs – still high over extended distance– Administration and maintenance costs

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Solutions – Major Categories

Disk mirroring synchronously – short distances Disk mirroring asynchronously

– with host data mover component– without host data mover component

Software-based replication and change propagation using logs – “shadowing”

Other software-based replication solutions– Peer-to-peer replication

Vaulting and journaling

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Synchronous mirroring:Disk subsystem-to-subsystem

e.g. IBM PPRC, EMC SRDF/S

Distance limitedapprox 100km

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Asynchronous mirroring:Using host data mover (e.g. IBM XRC)

Distance virtually unlimited

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Asynchronous mirroring:Disk subsystem-to-subsystem

e.g. IBM PPRC-XD, Hitachi HARC, EMC SRDF/A


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Database log

Log has after-images of changed records Sometimes only changed

fields or columns Used for forward/backward

recovery processes Concise basis for change

propagation Can be used for recovery or

replication

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Replication software-based:Using logs for change propagation


Workload balancing, data mining and replication

Replica copy can be “paused” at a point of logical consistency at any desired point in time

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Emerging trend: Peer-to-peer or “multi-master”

New York Node

West Coast Node Central Node

Multiple copies of the same database – all or some in update mode

Applications designed to tolerate ACID “fuzziness”

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Remote Vaulting

Production ServerVaulting Site

Recovery uses full backups Backups created (“vaulted”) at vaulting site Tape and/or disk backups maintained at vaulting site Channel extension technology

– Usually does not require host server at vaulting site

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Remote Journaling

Database logs/journals are sent to journaling site– One log file at a time – Or, continuous real-time remote logging using software

Journaling site has small server Recovery uses full backups plus database logs & journals

– Recovery possible to log truncation point Full backups sent off-site via courier or using vaulting solution

Production ServerJournaling Site

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DataLoss(RPO)

0

1 Day

1 Hour

1 Second

Recovery Time (RTO) 0 15 Minutes 6-24 Hours1-2 Hours

RPO/RTO and Daily Backups….

RPO – Recovery Point ObjectiveHow much transactional data is lost when an offsite recovery is required?

RTO – Recovery Time ObjectiveHow much time is required to perform offsite recovery?

Daily BackupsCTAM / Vaulting

Traditional

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DataLoss(RPO)

0

1 Day

1 Hour

1 Second

Recovery Time (RTO) 0 10 Minutes 6-24 Hours1-2 Hours

RPO/RTO for Advanced Solutions

Journaling (and/or Vaulting) Solutions

Asynchronous Database Replication

RPO – Recovery Point ObjectiveHow much transactional data is lost when an offsite recovery is required?

RTO – Recovery Time ObjectiveHow much time is required to perform offsite recovery?

Daily BackupsCTAM / Vaulting

Traditional

Asynchronous Disk Mirroring

Synchronous Disk Mirroring

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Relative Bandwidth Requirements

Time period: one weekS1 – software-based replicationS2 – hardware-based replication

S1S2

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Relative Cost Levels for Various Widely-Deployed Solutions

0

20

40

60

80

100

120

Tape w ithcourier

Remote tapeVAULTING

RemoteJOURNALING

Remotedatabase

shadow ing

Disk mirroringover shortdistance

Disk mirroringover longdistance

Relative Costs

CPU Memory

Disk Tape

Comm People

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New York Node

West Coast Node Central Node

Case study 1US Financial Services Industry

AA

A A BB

CC

CC

BB

DD E E F F

DD

E E

F F

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Case study 2US Securities Industry

Production Site

Backup Site #1 Backup Site #2Mirroring onlyShort distance

Vaulting, Journaling & Data replication over Extended Distance

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Next steps….

Analyze your organization’s requirements Engage multiple subject areas

– Disaster recovery– Operational management– Application design and deployment

Estimate costs for two or maybe three solutions Present best choices to management

Comdex Brasil August 2004 Storage Presentation

Documents

Transcript of Comdex Brasil August 2004 Storage Presentation