김병기 김병기 Senior Technology Specialistbgkim@microsoft.comMicrosoft Corporation

SQL Server 2000SQL Server 2000High AvailabilityHigh Availability

AgendaAgenda

What Is High Availability?What Is High Availability? HA TechnologyHA Technology Designing a Solution for HADesigning a Solution for HA

High AvailabilityHigh Availability

IsIs design, people, process ,technologydesign, people, process ,technology 의의

집합체집합체

오해…오해… .... technology solutiontechnology solution 이 아님이 아님 scalability scalability 또는 또는 manageabilitymanageability 와 유사한 와 유사한

개념이개념이 아님아님 ..

Breaking Down The NinesBreaking Down The Nines

Percentage Downtime (per year)Downtime (per year)

100% None

99.999% < 5.26 minutes

99.99% 5.26 – 52 minutes

99.9 % 52 m – 8 h, 45 min

99 % 8 h, 45 m – 87 h, 36 m

90% 788 h, 24 m – 875 h, 54 m

9

Hardware is well managedHardware is well managed• Can tolerate some hardware failuresCan tolerate some hardware failures

9Good management and planningGood management and planning

• Can tolerate most hardware failures Can tolerate most hardware failures • Can tolerate normal ops tasks (e.g., software upgrades)Can tolerate normal ops tasks (e.g., software upgrades)• Can tolerate some software failuresCan tolerate some software failures

9

Operational, planning, design excellenceOperational, planning, design excellence• Can handle most planned and Can handle most planned and unplanned downtime unplanned downtime • Can tolerate some operations failuresCan tolerate some operations failures

99UnmanagedUnmanaged

In S

um

mary

In S

um

mary

The Cost Of AvailabilityThe Cost Of Availability

99 99.1 99.2 99.3 99.4 99.5 99.6 99.7 99.8 99.9 100

Availability

Cos

t

AgendaAgenda

What Is High Availability?What Is High Availability? HA TechnologyHA Technology Designing a Solution for HADesigning a Solution for HA

Two Levels …Two Levels …

SQL TechnologySQL Technology Failover Clustering Failover Clustering Log ShippingLog Shipping ReplicationReplication

Windows TechnologyWindows Technology Windows ClusteringWindows Clustering NLB/WLBSNLB/WLBS

How Failover Clustering How Failover Clustering WorksWorks

Client PCs

Node A Node B

Shared Disk Array

HeartbeatSQL ServerSQL Server SQL ServerSQL Server

Log ShippingLog Shipping

SecondaryPrimary

Log Shipping Monitor

Transaction Logs

Log Shipping UsesLog Shipping Uses

H.A H.A 사용사용 :: Facilitate 7.0 Facilitate 7.0 2000 upgrade 2000 upgrade

원격지 서버원격지 서버문제 해결 방법 중 문제 해결 방법 중 failover clusterfailover cluster외의 또 다른 해결 방법으로 사용가능외의 또 다른 해결 방법으로 사용가능

Performing maintenance on PrimaryPerforming maintenance on Primary

Check DB healthCheck DB health

SQL HA Technology ComparisonSQL HA Technology ComparisonFeatureFeature Failover ClusteringFailover Clustering Log ShippingLog Shipping Transactional Transactional

ReplicationReplication

Failure detection

AutomaticAutomatic Not AutomaticNot Automatic Not AutomaticNot Automatic

Automatic switch to secondary

YesYes ManualManual ManualManual

Protects against failed server process

YesYes Yes, but …Yes, but … Yes, but …Yes, but …

Protects against failed disk

No, No, Shared-disk clusteringShared-disk clustering Yes, but …Yes, but … Yes, but …Yes, but …

Meta data support

All system and user schema and datAll system and user schema and data for all databasesa for all databases

Some system, all user Some system, all user schema and data for sschema and data for select databaseselect databases

Some user schema Some user schema and dataand data

Transactionally consistent

YesYes YesYes YesYes

Transactionally current

YesYes No, since last No, since last transaction log transaction log backupbackup

No, since last No, since last replicated replicated transactiontransaction

FeatureFeature Failover Clustering Log Shipping Transactional Replication

Performance impact

NoneNone Minimal (file Minimal (file copying on primary)copying on primary)

Log reader Log reader continually continually runningrunning

Time to switch Seconds to minutes, depends on Seconds to minutes, depends on db recovery timedb recovery time

Seconds, more to Seconds, more to recover more recover more thoroughlythoroughly

Seconds, more to Seconds, more to recover more recover more thoroughlythoroughly

Locations Close (unless using distance Close (unless using distance clusters on HCL)clusters on HCL)

Not location boundNot location bound Not location Not location boundbound

Additional complexity

SomeSome SomeSome MoreMore

Maximum number of servers

44 32 with NLB, 32 with NLB, otherwise no limitotherwise no limit

No limitNo limit

Standby available for reporting, etc.

N/A – not a warm standby N/A – not a warm standby solutionsolution

Yes. Possible Read-onlYes. Possible Read-only access when logs are y access when logs are not being loadednot being loaded

YesYes

Partitioning of data to standby

NoNo NoNo YesYes

SQL HA Technology ComparisonSQL HA Technology Comparison

AgendaAgenda

What Is High Availability?What Is High Availability? HA TechnologyHA Technology Designing a Solution for HADesigning a Solution for HA

모든 경우에 적용되는 완전한 모든 경우에 적용되는 완전한 guideline guideline 은 은 있있을 수 없다을 수 없다 ..

Make sure the technology is Make sure the technology is supportable in your environmentsupportable in your environment

Just because something is “cool” , it Just because something is “cool” , it may not be rightmay not be right failover clusteringfailover clustering 이 대부분의 경우에 이 대부분의 경우에

해당하는 해당하는 최상의 최상의 optionoption 이라 할지라도 이라 할지라도 , , 항상 올바른 선택은 아님항상 올바른 선택은 아님 ..

Picking The Right Picking The Right TechnologyTechnology

How Should I Deploy How Should I Deploy Replication?Replication?

ReplicationReplication 은 은 high availability solutionhigh availability solution 의 의 부분으로 이용될 수 있다부분으로 이용될 수 있다 .. 예를 들어예를 들어 , catalog data, catalog data 를 정기적으로 복제해야 하는 를 정기적으로 복제해야 하는

web siteweb site 의 경우의 경우 UpdateUpdate 가 점증적으로 발생하는 가 점증적으로 발생하는 DSS databaseDSS database 의 경우의 경우

It works very well for read-only dataIt works very well for read-only data

Load Load Balancing & Balancing & ReplicationReplication

Read only data Read only data Windows NT® Load Windows NT® Load

Balancing Service Balancing Service (WLBS) is used to (WLBS) is used to distribute the load distribute the load

Data is replicated to Data is replicated to multiple serversmultiple servers

LAN(Ethernet/FDDI)

IIS Server IIS Server IIS Server

Read-Only SQLServer

Read-Only SQLServer

NLB Cluster

NLB Cluster

Read/Write SQLServer

Publisher/Distributor

SN

AP

SH

OT O

R TR

AN

S R

EP

LICA

TION

SN

AP

SH

OT O

R TR

AN

S R

EP

LICA

TION

Public Network

Using Replication…Using Replication… ““continuous” mode replicationcontinuous” mode replication 로 운영시로 운영시

대기시간을 낮출 수 있음 대기시간을 낮출 수 있음 Watch for the exceptions Watch for the exceptions

(i.e., 10,000,000 row deletes)(i.e., 10,000,000 row deletes) 주의사항 주의사항

Only synchronizes what you requestOnly synchronizes what you request 추가의 변화 관리가 필요추가의 변화 관리가 필요 ..

절대 절대 backupbackup 의 대체 솔루션이 아님의 대체 솔루션이 아님

How Should I Deploy How Should I Deploy Log Shipping?Log Shipping? Planned failover scenarioPlanned failover scenario Secondary or remote failoverSecondary or remote failover logical failures + physical failureslogical failures + physical failures 에 에

대한대한 보호책으로 활용 가능보호책으로 활용 가능 저장 대상저장 대상 loglog 들에 대한 지연 들에 대한 지연 settingsetting 가능 가능

1 to 15 minutes is what we typically see1 to 15 minutes is what we typically see 1 minute for availability1 minute for availability 15 minutes or more for logical data 15 minutes or more for logical data

protectionprotection

NLB and Log ShippingNLB and Log Shipping One way to handle switching is via One way to handle switching is via

Windows NT® Load Balancing Service (WLWindows NT® Load Balancing Service (WLBS) BS)

설정설정 :: 22 개의 개의 log shipping SQL Serverlog shipping SQL Serveree 들간의들간의 a pria pri

vate network vate network 필요필요 LMHosts LMHosts 또는또는 WINS serverWINS server 를 통한 를 통한 resolve Iresolve I

P addresses P addresses 필요필요 정기적인 정기적인 sync master and msdb sync master and msdb dbdb 간의 간의 synsyn

cc 필요필요

NLB And Log ShippingNLB And Log Shipping

Switch NLB when primary goes downSwitch NLB when primary goes down Clients don’t have to know that they’re Clients don’t have to know that they’re

connecting to a new SQL Serverconnecting to a new SQL Server But the clients can’t depend on the But the clients can’t depend on the

server name eitherserver name either One solution: Use IIS server to point to One solution: Use IIS server to point to

SQL ServerSQL Server Problem: Problem: 중재안이 필요함중재안이 필요함

Better for planned failoverBetter for planned failover Consider using Data Dependent RoutingConsider using Data Dependent Routing

NLB, IIS And Log ShippingNLB, IIS And Log ShippingClients

NLB Cluster

PrimarySQL Server

SecondarySQL Server

DIP1

DIP2

DIP1

DIP2

Log Shipping

IIS Server

VIP

Log Shipping With Log Shipping With SnapshotSnapshotHardware-assisted solutionHardware-assisted solution Create database on standby with snapshot backup/restoreCreate database on standby with snapshot backup/restore Set up log shippingSet up log shipping Conventional log backups are copied over networkConventional log backups are copied over network

PrimaryPrimary StandbyStandby

Disaster Disaster Recovery SiteRecovery Site

Remote MirroringRemote MirroringSplit Split

Mirror Mirror

Deploying Failover Deploying Failover ClusteringClustering Secondary serverSecondary server 에 대한 에 대한 service levelservice level 을 결정을 결정

Do you need to be at 100% capacity after a Do you need to be at 100% capacity after a failoverfailover

Will help for software upgrades, hardware Will help for software upgrades, hardware upgrades, helps mask hardware faults…upgrades, helps mask hardware faults…

This will drive the decisions surrounding This will drive the decisions surrounding Single Instance or Multi InstanceSingle Instance or Multi Instance

N+1 clustering with Windows 2000 Data N+1 clustering with Windows 2000 Data Center Server (4 nodes)Center Server (4 nodes)

A Failover Cluster A Failover Cluster

VVirtual SQL Server(s)irtual SQL Server(s)

Private NetworkPrivate Network

Public Network(s)Public Network(s)

Node 1Node 2

Cluster Deployment: WinsCluster Deployment: Wins

Windows 2000 Data Center and SQL Windows 2000 Data Center and SQL Server 2000 can provide N+1 Server 2000 can provide N+1 failoverfailover

Note that 4th node could also Note that 4th node could also support an active instancesupport an active instance

Node1: Node1: AccountingAccounting

Node2: Node2: ResearchResearch

Node3:Node3:HRHR

Node4: Node4: SpareSpare

A “Distance” ClusterA “Distance” Cluster

Node 1Node 1

Disaster Recovery

Site

Remote Mirroring

Node 2Node 2

Node 4Node 4Node 3Node 3

New York CityNew York City ChicagoChicago

Primary Site

Log Shipping With Log Shipping With ReplicationReplication Replication can fail overReplication can fail over Typically you’d protect the publisherTypically you’d protect the publisher

PrimaryPrimary StandbyStandby

DistributorDistributor

SubscribersSubscribers

DistributorDistributor

SubscribersSubscribers

StandbyStandby PrimaryPrimary

Failover

Log Shipping With Log Shipping With ReplicationReplicationChoicesChoices Synchronous modelSynchronous model

+ Fault tolerantFault tolerant– Slower change propagation to Slower change propagation to

subscriberssubscribers Semi-synchronous modelSemi-synchronous model

+ Subscribers are updated as changes Subscribers are updated as changes occur occur

– Subscribers see duplicate changes in Subscribers see duplicate changes in some failure situations but replication some failure situations but replication designed to handle this nowdesigned to handle this now

Combining Log Shipping Combining Log Shipping And Failover ClusteringAnd Failover Clustering Protection against both logical and physical Protection against both logical and physical

failuresfailures

Log Ship Log Ship standby server standby server for each Virtual for each Virtual SQL ServerSQL Server

Secondary Secondary standby, for standby, for the truly the truly paranoidparanoid

Log Shipping Versus Log Shipping Versus Failover ClusteringFailover Clustering Failover clustering a good enterprise Failover clustering a good enterprise

solutionsolution Clients are unaware of failover since the Clients are unaware of failover since the

server name/IP address doesn’t change server name/IP address doesn’t change Single copy of dataSingle copy of data

Less synchronization issuesLess synchronization issues No data integrity concernsNo data integrity concerns

Requires specific expensive hardwareRequires specific expensive hardware

Log Shipping Versus Log Shipping Versus Failover ClusteringFailover Clustering Hot Standby has a separate copy of the dataHot Standby has a separate copy of the data

Provides for logical data protectionProvides for logical data protection Can be kept hours behind for more protectionCan be kept hours behind for more protection

Hot Standby need not be geographically Hot Standby need not be geographically closeclose

Can have multiple standby servers with Can have multiple standby servers with log shippinglog shipping

Clients may need to know name/location Clients may need to know name/location of log shipping serverof log shipping server Unless you use NLB/WLBSUnless you use NLB/WLBS Unless you handle this through Data Dependent Unless you handle this through Data Dependent

Routing (DDR)Routing (DDR)

Which One To Use?Which One To Use?

The most popular choice is the The most popular choice is the failover cluster, with a log-shipped failover cluster, with a log-shipped remote standby server. remote standby server.

Log Shipping is also often used for Log Shipping is also often used for reasons other than availabilityreasons other than availability

Replication can be used for availability Replication can be used for availability of read-only dataof read-only data

You can use all three together…You can use all three together…

SummarySummary

Microsoft SQL Server 2000 has several Microsoft SQL Server 2000 has several solutions to improve availabilitysolutions to improve availability Failover clustersFailover clusters Log shippingLog shipping ReplicationReplication

High availability is based on processHigh availability is based on process Pay attention to best practicesPay attention to best practices Practice Practice disaster recoverydisaster recovery Investigate Microsoft Operations Investigate Microsoft Operations

FrameworkFramework

Availability ResourcesAvailability Resources Best Practices in Change, Configuration and Problem ManaBest Practices in Change, Configuration and Problem Mana

gementgement http://www.microsoft.com/http://www.microsoft.com/mofmof

High Availability Operations Guide High Availability Operations Guide http://www.microsoft.com/NTServer/nts/deployment/planguide/Hihttp://www.microsoft.com/NTServer/nts/deployment/planguide/Hi

ghAvail.aspghAvail.asp Monitoring Reliability and Availability of Windows NT-based Monitoring Reliability and Availability of Windows NT-based

ServersServers http://www.microsoft.com/windows2000/library/operations/clustehttp://www.microsoft.com/windows2000/library/operations/cluste

r/monitorrel.aspr/monitorrel.asp Failover Clustering And Load BalancingFailover Clustering And Load Balancing

http://www.microsoft.com/windows2000/library/technologies/clushttp://www.microsoft.com/windows2000/library/technologies/cluster/default.aspter/default.asp

Network Load Balancing Technical OverviewNetwork Load Balancing Technical Overview http://www.microsoft.com/windows2000/library/howitworks/clustehttp://www.microsoft.com/windows2000/library/howitworks/cluste

r/nlb.aspr/nlb.asp

Availability ResourcesAvailability Resources

Capacity Planning for High AvailabilityCapacity Planning for High Availability http://www.microsoft.com/ISN/whitepapers/capacity_plannihttp://www.microsoft.com/ISN/whitepapers/capacity_planni

ng_for_ha_921.aspng_for_ha_921.asp Best Practices for End-to-End High AvailabilityBest Practices for End-to-End High Availability

http://www.microsoft.com/technet/avail/bestprac/http://www.microsoft.com/technet/avail/bestprac/bestprac.htmbestprac.htm

Planning, Deploying, and Managing Highly Planning, Deploying, and Managing Highly Available SolutionsAvailable Solutions http://www.microsoft.com/technet/avail/overview/http://www.microsoft.com/technet/avail/overview/

default.htmdefault.htm Monitoring Reliability and Availability of Windows Monitoring Reliability and Availability of Windows

2000 Servers2000 Servers http://www.microsoft.com/windows2000/library/opeartions/http://www.microsoft.com/windows2000/library/opeartions/

cluster/monitorrel.aspcluster/monitorrel.asp

Availability ResourcesAvailability Resources

Windows 2000 Reliability and Windows 2000 Reliability and Availability ImprovementsAvailability Improvements http://www.microsoft.com/windows2000/guide/platform/http://www.microsoft.com/windows2000/guide/platform/

strategic/relavail.aspstrategic/relavail.asp Cluster Strategy: High Availability and Scalability with IndusCluster Strategy: High Availability and Scalability with Indus

try-Standard Hardwaretry-Standard Hardware http://www.microsoft.com/ntserver/ntserverenterprise/exec/http://www.microsoft.com/ntserver/ntserverenterprise/exec/

prodstrat/cluster2.aspprodstrat/cluster2.asp Windows Clustering Technologies: Cluster Windows Clustering Technologies: Cluster

Service ArchitectureService Architecture http://www.microsoft.com/windows/server/technical/http://www.microsoft.com/windows/server/technical/

management/ClusterArch.aspmanagement/ClusterArch.asp Don’t forget Technet and MSDN…Don’t forget Technet and MSDN…

http://www.microsoft.com/technethttp://www.microsoft.com/technet http://msdn.microsoft.comhttp://msdn.microsoft.com