Download Building Highly Available Systems with SQL Server™ 2005

Building Highly Available
Systems with SQL Server™
2005
Robert Rea
Brandon Consulting
Availability
What does it mean to you?
 Why not?
Can your customers get done,
what they need to get done,
when they need to do it?
 Site is unavailable
 System is unavailable
 Database is unavailable
 Database is partially unavailable
 Table is unavailable
 Data is unavailable
24x7x365
Improved Data Availability
without Requiring Standby
 Downtime is reduced and/or prevented for
these barriers:
 Database is partially unavailable
 Table is unavailable
 Data is unavailable
Barriers to Availability
Isolated Failures
 Continuing to work with isolated failures
 Limiting the scope of failure
 Partial Database Availability
 Online Piecemeal Restore
 Supporting Technology
 Instant File Initialization
 How do they work?
What happens when…
 Disks Fail
 In SQL Server™ 2000
 Database is marked suspect
 Users are unable to access the database
 In SQL Server™ 2005
 Filegroup is marked offline
 Users are able to access undamaged data
What happens when…
 Recovery begins
 In SQL Server™ 2000
 Database is in a restoring state
 Users are unable to access the database
 File needs to be recreated and zero initialized
 File Restore can proceed – offline
 In SQL Server™ 2005
 Filegroup is in a restoring state
 Users are able to access undamaged data
 File can be recreated with instant file Initialization
 Piecemeal Restore can proceed – online
How is This Possible?
 Fine grained operations are based on “functional
partitioning”
 Partitioning – in this sense – does not require
Partitioned Tables
 Partitioned Tables benefit significantly from fine
grained operations
 Partitioning for fine grained operations requires
secondary, non-primary data files where data is
strategically placed
 Recovery of your damaged devices can be
prioritized and then the database can be brought
online in stages
Improving Data Availability
Partial Database Availability
What happens when…
 Indexes need to be rebuilt
 In SQL Server™ 2000
 Index rebuilds require an exclusive table-level lock,
resulting in offline rebuilds
 Users are unable to access the table
 In SQL Server™ 2005
 Rebuilds of an index can be performed online if a
few simple criteria are met
 Users are able to access the table
Online Index Operations
Improving Concurrency during Index
Maintenance
 SQL Server™ 2000
 Offline Index Rebuilds;
table data is unavailable
during operation
 Rebuild options: DBCC DBREINDEX and CREATE
with DROP_EXISTING
 SQL Server™ 2005
 Includes all of the above offline operations, plus…
 New ALTER INDEX…REBUILD:
 ONLINE – allows concurrent user access (queries as well as
modifications) to the index during rebuild
 OFFLINE – works using locks (same as SQL Server™ 2000)
 If online is not possible by default, consider design
alternatives to fully leverage online index rebuilds
Online Index Rebuilds
What happens when…
 Readers and Writers desire the same data
 In SQL Server™ 2000
 Locking is used to guarantee the intended level of isolation
 Users must wait to access locked data
 Concurrency and performance compromised
 Correctness is compromised when lower isolation levels are
used to avoid locking
 In SQL Server™ 2005
 Locking OR Versioning can be used to guarantee a variety of
isolation levels
 With versioning, Readers won’t block writers and writers won’t
block readers
 Performance improved if contention was primary bottleneck
 Correctness is not compromised due to use of lower isolation
levels
Snapshot Isolation
Improving Concurrency in Mixed
Workloads
 SQL Server™ 2000
 Isolation implemented solely through locking
 Mixed workloads may experience:
 Concurrency problems due to blocking
 The Inconsistent Analysis problem
 SQL Server™ 2005
 Isolation implemented using locking and versioning
 Mixed workloads can improve read consistency and
performance using:
 Read committed with Statement-level snapshot to improve
statement-level consistency
 Snapshot Isolation to improve transaction-level consistency
Snapshot Isolation
Barriers to Availability
People
I’m going to
modify this
data…right
…
here
!
This job would be great
if it weren’t for…
…the users
…the staff
…us
Barriers to Availability
Many more barriers than discussed
Only some are addressable by database technology
Be sure to consider people, planning, procedures and training
 Microsoft SQL Server™ 2005 gives you greatly
improved tools to overcome these barriers to
availability:
 Database Server Failure or Disaster
 Isolated Disk Failure
 Data Access Concurrency Limitations
 Database Maintenance and Operations
 Availability at Scale
 User or Application Error
Summary
 SQL Server™ 2005 offers greater
availability – immediately
 Many technologies available just by
upgrading!
 Some architected/implemented over time
 SQL Server™ 2005 is more Available
 Partially damaged databases remain available
 Databases being recovered remain available
 Instant File Initialization, Fast Recovery
 New and Improved Replication Alternatives
 SQL Server™ 2005 is more Robust
Customer Deployments
Gary Melvin,
Brandon Consulting
Customer Focus – BoS (Ireland)
 The Business Challenge
 Management information
reporting limitations
 SQL 2005 Benefits
 SQL Reporting Models
"Having completed our
evaluation of SQL 2005
we are very excited about
many of the new features
in SQL 2005 particularly
Integration services
and Reporting services.
We plan to incorporate
SQL 2005 into our
reporting
environment over the next
12 Months“
 Ad Hoc Reports
 Scheduled Reports –
Multiple Formats
Peter Brady IT Director Bank of Scotland Ireland
Customer Focus - ADM
 Business Challenge
 Data From Multiple
Systems And Formats
Required For Reporting.
 SQL 2005 Solution
 Data warehousing and
Reporting Solution
 Integration Services
 Multiple Formats Data
Imports and Translations
 Web Reporting
“We are planning to
standardize all our data
requirements using SQL
2005"
Noel Galligan IT Dept ADM
Customer Focus – Lifestyle Sports
 Business Challenge
 High Availability and
Disaster Recovery
 SQL 2005
 Increased
Performance and
Reliability
 Disaster Recovery
 Mirroring and
Replication
“SQL 2005 will give lifestyle
the level of performance
and reliability required to
run our business“
AM Keady Lifestyle Sports Operations
Customer Focus
General
- Europa
 "Having concluded that our


current reporting system
would restrict our growth, we
recognised that to thrive in a
very competitive market, it
was critical to our business to
Business Challenge
have technology that would
 Enterprise Information
enable us to grow. Brandon
Reporting
Consulting, using Microsoft’s
SQL 2005, is enabling us to
SQL 2005 Solution
consolidate our reporting
across our offices, at the
 Integration Services
same time as making us a
 OLAP – Database Design
more agile & responsive
business."
 Scheduled Reporting
 Brian McGrady IT Manager
 Add Hoc reports
Europa General
 Web based Reporting