Configuring a Windows Azure SQL Sync Group · PDF fileConfiguring a Windows Azure SQL Sync Group 4 Introduction to SQL Azure In this first chapter, I’m going to briefly explain SQL

Configuring a Windows Azure

SQL Sync Group

Provide Cross-Region Data Protection

Introduction Windows Azure is a truly amazing platform for consumers of IT services. It provides enterprises from

the small sole trader business through to global conglomerates the ability to quickly and effectively

consume cloud services but also allows you to so with ease.

New features and service offerings are appearing with rapid pace as Microsoft seek to make Azure

the glove that fits for everyone and the prices keep on coming down too which makes it more

affordable to consume cloud than ever before.

In this guide, I’m going to walk you through the process of setting up Windows Azure SQL Sync

between two SQL Azure databases. This technology using Windows Azure SQL allows you to

replicate databases either between other instances of Azure SQL databases or with on-premise SQL

Server databases.

This guide as are all my publications, dedicated to my wife Nicky and my three daughters; Madison,

Jessica and Layla who are subjected to living with me and technology and not always in that order.

Authors Richard J Green works as a Senior Technical Consultant for Infront Consulting, specializing in

delivering System Center solutions helping customers leverage their investment in IT with Microsoft

technologies. Richard works extensively with Windows Azure and System Center.

He has an unhealthy obsession with the colour pink hence the colour choice of this book.

You can follow Richard on Twitter @richardjgreen or read his blog focusing on Microsoft products

and technologies along with other digital ramblings at http://richardjgreen.net.

Copyright This book is copyright of Richard J Green and co-authors. No unauthorised copying of material in this

book shall be performed without the prior written consent of Richard Green or one of the co-

authors.

© 2014

http://twitter.com/richardjgreen

http://richardjgreen.net/

Contents Introduction ...................................................................................................................................... 2

Authors ............................................................................................................................................. 2

Copyright .......................................................................................................................................... 2

Introduction to SQL Azure ................................................................................................................. 4

What is SQL Azure?........................................................................................................................ 4

How is it Different to SQL Server? .................................................................................................. 4

Why Would I Use it Verses SQL Server? ......................................................................................... 5

Introduction to SQL Azure Sync ......................................................................................................... 6

What is SQL Azure Sync ................................................................................................................. 6

SQL Server Log Shipping Features .................................................................................................. 6

SQL Azure Sync Features ................................................................................................................ 6

Prerequisites for Configuration .......................................................................................................... 8

Configuring SQL Azure Servers ........................................................................................................... 9

Configuring SQL Azure Databases .................................................................................................... 12

Creating a Sync Group ..................................................................................................................... 13

Define Sync Group Rules .............................................................................................................. 17

Configure Automatic Sync ............................................................................................................ 21

Checking the Status of the Sync Group ............................................................................................ 23

Configuring a Windows Azure SQL Sync Group

4

Introduction to SQL Azure In this first chapter, I’m going to briefly explain SQL Azure, what it has to offer and the limitations of

it over conventional SQL Server. I’m not going to get hung up on pricing here as this will vary

according to your agreements with Microsoft and what kind of commitment you make to Windows

Azure however I will touch on pricing at a high level.

What is SQL Azure? SQL Azure offers up database as a service (DBaaS). This DBaaS allows us to provide customers of our

services with a database to allow applications to store data without the concern or overhead of the

underlying database server.

SQL Azure does still rely on the concept of a database server, however this is for the most part

transparent to us. The only time we actually interact with the server is in two ways:

1. Accessing the server to manage or connect to databases using the server username and

password combination

2. Creating new databases in a specified server

SQL Azure is a regionalised service allowing us to create databases in any of the Windows Azure

regions of our choosing, allowing us to be both flexible and efficient. With this, we can home the

database in the most appropriate location with regard to our application.

How is it Different to SQL Server? The principles and concepts applied to a SQL Server and databases remain the same. A server can

host many databases. A database can have many tables, tables have many columns and rows and so

on.

The major hang-up for administrators of SQL Server platforms is centred on the sizing and

performance of those servers and this is where SQL Azure differs.

With a conventional SQL Server software, database administrators and platform engineers will

concentrate on ensuring that the server has the right amount of everything to meet the

performance expectations.

Memory to allocate to the SQL Server processes

Enough CPU sockets and cores to cope with the processing demand

Sufficient I/O per Second (IOPS) in the disk architecture and hardware

Correct RAID levels to provide appropriate protection for databases and logs

Such is this configuration complexity and challenge for SQL Server that companies such as Fusion-io

have made an entire business of developing flash based interface cards for servers to provide

massive IOPS for platforms just like SQL Server.

This is just a subset of the challenges faced by engineers designing SQL Server platforms and this is

the reason SQL Azure is a wonderful solution.

No more do we need to worry ourselves about whether a SAS 6Gbps RAID10 vs. iSCSI or Fibre

Channel storage will provide enough bandwidth for our databases or whether an Intel E5-2450 vs. an

Intel E5-2660 is the right processor.

With SQL Azure, when you decide you want a database, you pick a name for it and whether you

want to use the Web or Business scale for it and deploy. The only question that needs answering is

Introduction to SQL Azure

5

which collation you opt for and that is normally chosen for you by the application so this decision is

reduced to reading up the correct value in the software vendor’s documentation.

Why Would I Use it Verses SQL Server? Price and simplicity are the two key factors in this decision. To build and configure a SQL Server with

the appropriate hardware to meet performance expectations and requirements coupled with the

licensing requirements for SQL Server licenses, it can be costly to do.

The complexity of getting the configuration right taking into account the hardware, operating

system, SQL Server software, authentication, backup and more can be overwhelming too.

If you are working for a company which has openly adopted cloud and have extended your on-

premise datacenter to the cloud using Windows Azure Infrastructure as a Service (IaaS) with

Windows Azure VPN you may be thinking that you can avoid the configuration complexity by just

provisioning an A5, A6 or A7 virtual machine in Windows Azure which is indeed true however the

Service Provider Licensing Agreement (SPLA) for SQL Server in Windows Azure is still pretty

expensive.

SQL Azure is billed on storage consumption of the database. An example 10GB database in either the

Web or Business services will cost you just under £30 per month. A SQL Server using the A6 IaaS

Virtual Machine size could be costing you £400 a month to host the very same database.


6

Introduction to SQL Azure Sync In this section, I’ll cover what SQL Azure Sync is and how it can help you.

What is SQL Azure Sync Those of you verse in traditional SQL Server availability and data protection technologies will be

familiar with terms such as Mirroring, Log Shipping, Clustering or AlwaysOn. All of these offer a

different way to protect your data and SQL Azure Sync is a new take on this, taking some of the best

elements of each, and offering it up in a way which makes it easy to consume as you would expect

from a DBaaS cloud service.

If you were to compare SQL Azure Sync to an existing SQL Server technology, it is closest to Log

Shipping.

SQL Server Log Shipping Features With Log Shipping you are required to have multiple separate SQL Servers which transport

transaction logs from the server with the database copy designated as the Primary. These logs are

sent to one or more servers which are designated as Secondary’s of which there may be more than

one.

Log Shipping permits for a user-specified delay between the transmission of the logs allowing a

Secondary database to be kept intentionally out of sync for a configurable period of time. This can

be an ideal configuration to protect against data corruption. Having the Primary and Secondary in a

near real-time configuration provides excellent availability for the data under normal conditions

however if something corrupts data in the Primary database, you will be left running for your DPM

Central Console to recover the database from a previous backup (you are using System Center Data

Protection Manager 2012 R2 to backup your SQL Servers right).

Log Shipping when configured, allows for the use of a limited degree of read-only access from the

Secondary databases. This limited read-only access allows applications which are Log Shipping aware

to perform read operations from a Secondary database which may be closer to or better connected

to the application that the Primary although this would normally only apply in the case of a highly

distributed application as you wouldn’t typically architect an application to sit further from its

Primary than it does its Secondary.

SQL Azure Sync Features The good news firstly is that everything Log Shipping can do, SQL Azure Sync can do and some.

At a high level, here are the key features and benefits of SQL Azure.

Multi-Master Model

Conflict Detection

N-Node Architecture

User-Specified Delay Support

Granular Synchronisation

Multi-Master Model refers to a key difference between SQL Azure Sync and SQL Server Log Shipping

to the benefit of SQL Azure Sync. Whereas Log Shipping has a single Primary with multiple

Secondary’s, SQL Azure allows you to deploy bi-directional synchronisation between databases and

using Conflict Detection, SQL Azure Sync is able to determine which database update wins in the

event of a tie.

Introduction to SQL Azure Sync

7

An N-Node architecture matches the capability of Log Shipping allowing you to have a large number

of databases synchronising the same database content to make your database as distributed or

available as you require however with SQL Azure Sync, unlike SQL Server Log Shipping, these

multiple nodes are fully readable and writable in to and from any of the databases in the group.

User-Specified Delay as before, is matched by the Log Shipping feature allowing you to configure a

time delay between automatic synchronisations occurring between Sync Group members. Keep in

mind with SQL Azure Sync however that if you are planning on taking advantage of the ability to

perform read and write operations in any of your database locations that you might not want to use

a delay between the database copies as this could result in differing results for clients or applications

accessing the database due to differences between the data sources.

The advantage that SQL Azure Sync has over all other SQL Server technologies is Granular

Synchronisation. This ability means that you are fully in control of what data subsets are important

to you and warrant being kept copied in another database elsewhere in the world. If you have a

multi-gigabyte database but only a single table or even a single column in a single table are truly

important to you, then you only need to sync this subset of items. This capability means that not

only can you reduce the time it takes to converge databases between copies but also reduces your

Windows Azure storage expenditure as you will only be paying for storage for the amount that you

are consuming through sync to other database copies.


8

Prerequisites for Configuration The prerequisites for the configuration of SQL Azure Sync are actually pretty limited. In this guide, I

am solely focusing on the ability to make your Windows Azure SQL databases available across

datacenter regions, however in a future guide, I plan to unearth the ability to combine SQL Server

with SQL Azure using this technology. In that guide, we will have more to research and work on with

prerequisites, however for now, bare the following in mind.

1. Access to a Windows Azure Subscription which allows you to create new objects such as new

SQL Azure Servers and Databases

2. Sufficient spending limit entitlement remaining in the subscription to create the required

databases if your subscription is capped to a budgetary limit

For the remainder of this guide, I am assuming that you currently have no SQL Azure Servers or

Databases configured and I will walk you through the process from end-to-end.

Configuring SQL Azure Servers

9

Configuring SQL Azure Servers Before we can do anything else in this guide to work on SQL Azure Sync, we need a SQL Azure

Server, two for this example to be more specific.

As I have pointed out previously, SQL Azure Sync allows us to create an N-Node Sync Group but for

this guide I will be demonstrating the simplest possible configuration with two servers and two

databases.

Once you’ve got yourself logged into your Windows Azure Portal, select the SQL Databases node

from the navigation on the left. This will open the SQL Databases panel. From the ribbon menu at

the top, select the Servers option and then select the option at the bottom for Add.


10

First off, we want to create a SQL Server in our primary region, the region where our application that

uses the SQL database is going to be located. For me, this is North Europe so I select the North

Europe region from the bottom of the Create Server dialog. You need to specify a Login Name, Login

Password for the SQL Server and also which subscription it should be setup in if you have more than

one subscription accessible to you. The login that you create is a SQL Login for those of you familiar

with Windows Authentication vs. SQL Authentication.

With all of the fields entered, select the tick button in the bottom right of the dialog to create the

server. Servers are created in Windows Azure with a random ID name which you have no control

over if you were wondering why you weren't asked to enter a server name in the previous dialog.

With that server created, we now want to create the secondary server for our alternate datacentre

region.

Select the Add button again from the bottom of the SQL Databases Servers view.

Configuring SQL Azure Servers

11

For simplicity and to make troubleshooting easier, I like to have my username and password on my

primary and secondary servers matching but that's a choice for you to make. Enter the Login Name

and Login Password that you wish to use and select the subscription if required. Lastly, specify your

region as that which you wish to use as your secondary. I elected to use West Europe. North Europe

is in Ireland and West Europe is in Amsterdam so that's plenty of miles between the two for my data

to be safe in the event of a disaster in one location to not affect the other, unless ash clouds can

bring down datacenters as well as keep planes on the ground of course.


12

Configuring SQL Azure Databases With our SQL Servers created, we can now create databases on those servers. From the SQL

Databases view in the Windows Azure Portal, select the Databases option from the top ribbon

menu. Select the New button in the bottom left, and from the popup menu, select the Data Services

> SQL Database > Custom Create option.

From the New SQL Database Custom Create wizard, enter a name for the database. From the

Edition picker, select either Web or Business. I use Web for my database as my current database is

about 15MB so there is no way it's going to hit the ceiling of 5GB on Web edition any time

reasonably. 5GB is the limit for Web with the default size being 1GB. Business has a default size of

10GB and scales up to 150GB. You can alternate between Web and Business after the fact so I would

select Web if you are starting out with this.

The next option is Collation. Select this option wisely as you cannot change it once the database is

created. The default collation is SQL_Latin1_General_CP1_CI_AS however I am using the Windows

collations right now so I’ve selected to use Latin1_General_CI_AS. The Microsoft Support article at

http://support.microsoft.com/kb/322112 explains that SQL collations are retained for backward

compatibility and that Windows collations are preferred. There are a few small performance

differentiators between the two so please do read the article if you are unsure. Furthermore, if you

are unsure what CI_AS means or whether you need case, accent, kana or width sensitivity or

insensitivity for your database, please refer to the support documentation for your product or if no

documentation or advice on collation is provided for the product, refer to the MSDN documentation

http://support.microsoft.com/kb/322112

Creating a Sync Group

13

at http://msdn.microsoft.com/en-us/library/ms143515(v=sql.105).aspx. If all the above fails, then

use the default of either SQL_Latin1_General_CP1_CI_AS or Latin1_General_CI_AS as above.

As before, select the appropriate subscription if you have multiple available to you. You will need to

select the same subscription as that which you created the SQL Server into previously. The final

option is Server. For this first database, select the Server which you created in your primary region,

North Europe for me as shown in the screenshots.

Once you have your database created, repeat all of the above steps to create the secondary

database. I like my primary and secondary databases to have the same name just for ease of

management and consistency but there is no rule which says you must do this. You could append

your names with _primary and _secondary to differentiate them if you like but this makes things

challenging if you are in a failover scenario later on where your secondary actually becomes your

primary. For the secondary database, make sure you select the server in your secondary region

which for me is West Europe.

Creating a Sync Group With our two SQL Servers and our two SQL databases now created in our two distinct regions, we

are ready to create a Sync Group between them. From the SQL Databases view of the Windows

Azure Portal, select the Add Sync option from the bottom and select the New Sync Group sub-

option.

This will launch the Create SQL Data Sync Group wizard.

http://msdn.microsoft.com/en-us/library/ms143515(v=sql.105).aspx


14

On the opening screen, enter a Name for the Sync Group. I have named my group in accordance

with the database name but replacing the db suffix with the sync reference. For the Region option,

set this to the region of your primary database which for me is North Europe once more. As

previously, select the appropriate subscription if you have multiple available to you. This needs to be

the same subscription as the SQL Servers and databases previously created.


15

Next, we define the Sync Hub. The Sync Hub is the database which will be used as the dataset

source, the primary database. From the drop-down menu for the Hub Database option, you will see

your two newly created databases. Make sure you select the correct database which for me is the

database in North Europe. Once the database is selected, enter the Username and Password for the

SQL Login that you specified when you created the SQL Server. This will be validated with a green

check in the Hub Password box if correctly entered.

The final option for Conflict Resolution is probably the most important here. The two choices are

Hub Wins and Client Wins. This settings refers to what occurs in the situation where both the Hub

and Client (Reference) databases have an update to a table row and which database should win the

tie. I use Hub Wins for my situation because I am only using the Reference database as a passive

copy and I am not actively writing to it therefore any writes to the Reference for me are to be

considered fraudulent or a breach of the SQL Server security and an attempt to compromise the

database integrity.


16

The final step in the SQL Data Sync Group wizard is to define the Reference database. Not as the

name would suggest, this is the database which is used as the replica, the copy, mirror or whichever

turn of phrase you prefer to use.

Select the database from the Reference Database picker and ensure you select the database in your

secondary region, West Europe for me. Enter the Username and Password as per your SQL Server

configuration and verify that the password is validated with the green tick. The final option is to

specify the Sync Direction. The three available options are Bi-Directional, Sync to the Hub or Sync

from the Hub. This option dictates the data flow through the Sync Group. In a simple setup like my

own, I use Sync from the Hub ensuring that the Hub is the primary database and that the replica

copy in the secondary location receives updates from the Hub. If your design was utilizing the Sync

Group as a multi-read multi-write configuration then you would want to use Bi-Directional.

Select the Sync Direction option carefully to match the technical design for data flow within your

solution. Selecting the wrong option could result in your application either not being able to write to

SQL or could see inserts and updates to table rows being discarded during a sync update.

Once you have completed the wizard, you will be taken to the SQL Databases Sync view in the

Windows Azure Portal as shown below.


17

The Sync Group will be shown as created but the status will be Not Ready as we now need to define

the settings for the sync relationship by determining which parts of the database schema are

included or excluded.

Define Sync Group Rules To begin making the Sync Group work for you, click it from the SQL Databases Sync view and select

the Sync Rules tab from the ribbon menu.


18

Start off by clicking the Define Sync Rules option in the middle of the screen. This will open the

Define Dataset dialog.


19

Here we need to select the database which will be used as the initial seed database.

It's important to note that your seed database needs to have a schema consisting of tables and

columns already in place. If you make any changes to the schema in the once the Sync Group is

configured, you will need to review the configuration of the Sync rules on the database and update

the Sync Group with these changes. As this example is a WordPress database install, there is little of

that happening for me to worry about.

Select the database in your primary region, North Europe for my example then select the tick to

have Windows Azure read the schema from that database.


20

The schema for the selected database will now be shown. From now on in, we can be super granular

with how we sync the database or we can just throw everything at it. I want the whole database to

be in sync so I am going to be showing you how to sync everything but you could be a little more

picky than I am in your scenario.

Click the Select option from the bottom of the page and then select the Select all the columns in all

the tables sub-option. This will check every column in all of the tables to be included in the sync

relationship. Select the Save button at the bottom to configure this as the Sync Rule for this Sync

Group.

Clicking Save will not only save the configuration but will start the initial seed sync of the databases.


21

Configure Automatic Sync Once the above is complete, we want to click the Configure link in the ribbon top menu. On the

Configure tab, under the General heading, there is a setting option for Automatic Sync.


22

Select the On option for Automatic Sync and then under the Sync Frequency option set an

appropriate interval in Minutes, Hours, Days or Months. Your setting for this will vary according to

how rapidly you want the two databases to converge any changes and how quickly data in your

databases is subject to change. I have my databases set for every 12 Hours.

Synchronising the databases will incur costs as inter-region traffic within Windows Azure is a billable

item. A high frequency synchronisation setting will incur more cost than a low interval so you need to

balance your technical goals against the costs.

Select the Save button to save the changes and to enable the Automatic Sync.

Checking the Status of the Sync Group

23

Checking the Status of the Sync Group Once all of the above has been completed, the Sync Group should now be working away. An

automatic initial sync occurs once you define the Sync Rules which depending on the size of your

database will have already completed by now. Select the Properties link from the top ribbon menu

and you will see the current configuration settings for the Sync Group including the health status and

the time of the last sync.

As you can see, my Sync Group is reporting Good health status and everything looks to be working

but to be sure, we can take a look at the Logs view from the ribbon menu.


24

From the Logs view, we can see the event log for the Sync Group. My log has three events to report

that the databases were successfully provisioned and that a sync successfully completed, verifying

that my good health status is indeed good.

With all that done, you've now successfully setup a Windows Azure SQL Data Sync Group. As you can

see, it's not actually that complicated to setup but it's just a matter of getting things done in the

correct order. I hope this helps and I'll be sure to post more about this feature as I use it more for

myself.

Documents

Configuring a Windows Azure SQL Sync Group · PDF fileConfiguring a Windows Azure SQL Sync Group 4 Introduction to SQL Azure In this first chapter, I’m going to briefly explain SQL