steeleye™ datakeeper™ for windows - module 1:...

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Module 1: Concepts

Learning Objectives

At the end of this module, the student will understand:

Why DataKeeper is a critical ingredient to business continuance

DataKeeper’s features and benefits

General and specific terms related to data replication and DataKeeper

Common DataKeeper replication configurations

The architecture of DataKeeper

How synchronous and asynchronous replication work

August 10 Copyright © 2000-2010 by SteelEye Technology, Inc. All Rights Reserved. 2

Why Automate Data Protection?

Lost revenue when data is not available

Costs associated with manual data recovery

Business processes require:

• Data to be continuously available

• Data to be continuously protected


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Costs Associated with Data Loss

Types of LossAverage Cost of Each Data

Loss Incident

Technical services 340.00

Lost productivity 217.00

Value of lost data 3,400.00

Cost per Incident $3,957.00

Number of incidents in 2000 4,607,100

Total US Data Loss Costs $18,230,294,700.00

Total US Data Loss Estimates Sources:

Graziadio Business Report

Network Computing

Data is an Asset

What will it cost if a business looses access to its data?

What if that loss is permanent?

What are the Recovery-Point and Recovery-Time objectives?

• Do current backup and recovery processes meet these objectives?


DataKeeper™ Features and Benefits

Features Benefits

• Block Level Replication • Eliminates single point of failure

(shared disk subsystem)

• Application agnostic; no need for

application-aware agents

• Support of both synchronous and

asynchronous replication

• Choice of replication method

optimized to minimize potential data

loss while working effectively in low

latency local-area networks or

higher latency, wide-area networks

• Support for multiple mirrors and

targets

• Flexibility in data placement for

optimum performance

• Ability to replicate both locally and

remotely

• Persistent bitmap • Fast, partial resynchronization

• White-Space Elimination • Unused blocks are not replicated


DataKeeper™ Features and Benefits


Features Benefits

• Exclusive use of Windows’ TCP/IP

stack for replication

• Eliminates sensitivity to network

latency

• Compression (nine levels) • Optimize bandwidth consumption

• Bandwidth throttling • Allocate bandwidth allowing efficient

support other networked

applications

• Scriptable • Continuous, scheduled or periodic

replication

When combined with high availability clustering:

Automated data and application protection

Automated failover

Support for both shared and replicated volumes

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Features in More Detail

Replication

Full volume replication

Sector by sector

Target(s) locked

• Replication engine requires exclusive control of volume

• Guaranteed write order sequence

• Maintains data integrity

NTFS Access Controls are preserved


Features in More Detail

Compression

Nine levels of compression

Turning compression on typically offers greatest benefit (up to 30% boost in bandwidth efficiency)

Throttling

Allows capping bandwidth used

Good for multi-use links when replication and client traffic need to use the same connection


Product Editions

DataKeeper™ Standard Edition

Replicate any data volume

Plugs into SteelEye LifeKeeper™ to provide high availability for any program, service or application

DataKeeper™ Cluster Edition

Replicate any data volume

Plugs into Windows Server Failover Clustering to provide high availability for any Microsoft supportable resource


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Supported Platforms

Windows Server 2003/R2

All editions

32-bit and 64-bit

Windows Server 2008

32-bit and 64-bit

Windows Server Core

Windows Server 2008 R2

64-bit

Windows Server Core

Hyper-V Server 2008 R2

64-bit


DataKeeper™ with LifeKeeper®

Combined Features

Support for all Windows Server Editions (excluding SBS and EBS)

Does not require Microsoft Enterprise Edition applications

High Availability

• Minimize unplanned outages; managed planned maintenance windows

• Automatic fault detection and recovery provided by LifeKeeper

• Shared storage not required, but supported

Disaster Recovery

• Shared storage not required, but supported at primary site

• Co-location of servers not required

Application Recovery Kits

Replication is fully integrated with all kits

Exchange requires an IP address, and DNS for WAN environments


DataKeeper with Microsoft Cluster Services or Windows

Failover Clustering

Combined Features

Support for in Windows Server Enterprise and Data Center Editions and Hyper-V Server 2008 R2

High Availability

• Minimize unplanned outages; managed planned maintenance windows

• Automatic fault detection and recovery provided by MSCS/WSFC

• Shared storage not required, but supported

Disaster Recovery

• Shared storage not required, but is supported at all sites

• Co-location of servers not required

Microsoft clustering provides transparent computer name failover

Extensive Enterprise Application Support


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DataKeeper™ Concepts

Terminology and Definitions


Windows Storage Terminology

Disk Types

Basic – classic MS-DOS/Windows disk type

Dynamic – logical volume and software RAID0 and RAID1

Volume Types

System - Windows boot disk and/or disks containing page files

Mirrored - Local disk configured in DataKeeper™

Non-Mirrored - Local disk NOT configured in DataKeeper™


Replication Terminology

Synchronous replication

Slower - subject to network latency

Data always in-sync, no lost transactions

• Target write confirmed first

• Source data written

Write sequence guaranteed unless resynchronizing


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Asynchronous replication

Faster - writes queued to target

• Data passed to local disk subsystem

• Simultaneously sent to target(s)

Persistent bitmap file maintains state of writes queued, but not acknowledged.

Possibility of lost transactions, but not data integrity

• Write sequence guaranteed unless resynchronizing



Replication endpoints – mirror roles

Source – mirrored volume is accessible

Target – mirrored volume is locked

Rate of Change

Irrespective of total volume size

Only the data that’s actually changing is replicated

Measuring the rate of change

Process – Performance counter – Write Bytes/sec

Time frame


DataKeeper™ Terms

Job

Container for one or more mirrored volumes

Volume

Replicated data disk

Must appear in Windows disk manager

Must be assigned a drive letter

May not be marked with the Windows “System” attribute

May not contain a Windows page file


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DataKeeper™ Terms

Bitmap File

A persistent binary file maintained on the source system for each mirror

Each bit in the bitmap file represents one block of the volume replicated

The corresponding bit is turned on whenever the associated block is modified.

The corresponding bit is turned off when the write has been acknowledge as having been successfully written by the target server


DataKeeper™ Terms

Asynchronous Write Queue / Intent Log

A memory-resident, time-ordered list of blocks to be replicated

Allocated from Windows Non-Paged Memory

Size is limited in 32-bit Windows environments (256MB)

• Use caution with /3GB switch as it reduces the maximum amount of non-paged memory to 128MB

High Water Mark

• The point in the asynchronous write queue when, if exceeded, DataKeeper goes into a pause/resynch cycle

Low Water Mark

• The point in the asynchronous write queue when reached during a pause/resynch cycle that triggers DataKeeper to put a mirror back into mirroring state


DataKeeper™ Terms

Mirror States

State Meaning

Resynchronizing 1. Data is being synchronized between source and target.

2. Data integrity of target not guaranteed while in this state.

3. State during initial mirror creation.

Mirroring 1. Normal state. Data integrity guaranteed at all times.

Paused 1. No data transmission between source and target.

2. Writes on source are tracked by in-memory and persistent

bitmap file on disk.

3. Partial resynchronization occurs after mirror is continued

with only the data changed during paused state being

transmitted to target.

Broken 1. No data transmission between source and target.

2. Writes on source are not being tracked.

3. Full resynchronization required after mirror reestablished.


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Common DataKeeper™ replication scenarios/configurations


Common Replication Configurations

One-to-One

Source

Server

Mirror Source

Target

Server

Mirror Target

Replication

Volume X: Volume X:

Switchover



One-to-Many (Multiple Targets)

Source Server

Target Server

Replication

Mirror 2 - Target

Volume X:

Target Server

Mirror 1 - Target

Volume X:

Mirror

Source

Volume X:


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Many-to-One

Target Server

Source Server

Replication

Source Server

Mirror 1 - Source

Volume X:

Mirror 2 - TargetVolume Y:

Mirror 1 - TargetVolume X:

Mirror 2 - Source

Volume Y:



N-Shared-Disk-to-One

WAN/LAN

Replication

Primary Site Remote Site

Shared Source Volume

Volume X:

Shared

Storage

Target Volume

Volume X:

Source

Server

Target

ServerFailover

Site Failover



N-Shared-Disk-to-N-Shared-Disk

WAN/LAN

Replication

Primary Site Remote Site

Shared Source Volume

Volume X:

Shared

Storage

Source

ServerFailover

Site Failover

Shared Target Volume

Volume X:

Shared

Storage

Target

Server

Windows

Server

Failover

Cluster


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N-Shared-Disk-to-Multiple-N-Shared-Disk

Replication

Shared

Target 1

Volume X:

Shared

Target 2

Volume X:

Shared

SourceVolume X:

Site A

Site B Site C

Windows Server

Failover Cluster

Protecting Hyper-V

Virtual Machines



Architecture



Architecture

DataKeeper

GUI

Command Line

Interface

(EMCMD)

DataKeeper Service

(ExtMirrSvc.exe)

Windows

Applications

NTFS.SYS

DataKeeper Filter Driver

(ExtMirr.sys)

Volume

( X: )

User Mode

Kernel Mode

Network

Replication Traffic


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Graphical User Interface



Understanding How Synchronous and Asynchronous Replication Work


Synchronous Replication

Application

Bitmap file

1

4

3

2

Write Request 2

Write Request 1 (complete)

IO Copy

Write Queue

Network

Source Volume

Target Volume

5


12

Asynchronous Replication (1)

Application

Bitmap file

1

2

4

3

Write Request 2

Write Request 1

IO Copy

Async Write Queue

HighWater LowWater

9600 50

Network

Source Volume

Target Volume

Note High and Low

“Water” Marks in Asynch

Write Queue



Application

Bitmap file

1

2

4

3

Write Request 3



IO Copy

Async Write Queue

HighWater LowWater

9600 50

Network

Source Volume

Target Volume

5



Application

Bitmap file

1

2

4

3

Write Request 3

Write Request 2


IO Copy

Async Write Queue

Network

Source Volume

Target Volume

5

Write activity exceeds

the “High “Water Mark”.

Mirror is paused and

resynchronized. When

the “Low Water Mark” is

reached, the mirror

returns to Mirroring state.

HighWater LowWater

9600 50


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Asynchronous Replication – Mirror Paused

Application

Bitmap file

1

2

IO Copy

Async Write Queue

HighWater LowWater

9600 50

Network

Source Volume

Target Volume


Asynchronous Replication – Resynchronization (1)

Application

Write Queue

HighWater LowWater

9600 50

Source Volume

1 2

3

4

Target Volume

34 12

Read bitmap file

sequentially to find

each modified bit

2

Write Request 4

Write Request 3

Write Request 2

Write Request 1

Netw

ork

Bitmap file

1 2

3

4

1

Read each modified

block from source

volume and copy to

write queue

3

Send block to target

driver



Application

Write Queue

HighWater LowWater

9600 50

56

Blocks modified after their bit has been read

will be picked up in next bitmap file scan

1

2

Netw

ork

Blocks written by

application are

flagged in bitmap and

written to source

volume

3

Send block to target

driver

Write Request 6

Write Request 5





Target Volume

4

Target driver sends

write

acknowledgement to

source driver

Bitmap file

5 6

Source Volume

5 6


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Application

Write Queue

HighWater LowWater

9600 50

Continue re-reading

bitmap file

sequentially, until all

bits are clear.

Target Volume

Netw

ork

Bitmap file

Source Volume







1



Application

IO Copy

Async Write Queue

HighWater LowWater

9600 50

Target Volume

Write Request 8

Write Request 7







1

2

3

Bitmap file

Source Volume

Netw

ork4

5



Summary


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Key Points

Organizations should recognize that protection of data is a critical component of business continuance.

Organizations should understand all repercussions and costs associated with a data loss incident.

DataKeeper is a critical component to any data protection or high availability environment.

DataKeeper provides fast and efficient block-based replication.

DataKeeper supports both synchronous and asynchronous replication, providing the highest data fidelity with the most optimized network utilization characteristics.

DataKeeper includes features that optimize and conserve the use of bandwidth in wide area network-based replication environments.


Key Points

When cost is a concern, DataKeeper eliminates the requirement to purchase, deploy and support expensive shared storage devices when implemented with either SteelEye LifeKeeper or Windows clustering products.

Where shared storage is already present, DataKeeper supports its use for both source and target volumes with Microsoft clustering and for source volumes with SteelEye LifeKeeper.

DataKeeper allows extension of SteelEye LifeKeeper and Windows clusters over multiple, geographically-dispersed networks.

DataKeeper supports a wide set of possible replication configurations.


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