Designing Data Storage Architecture-the data storage offerings available on the Windows Azure platfo
2011-12-28 22:20
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http://social.technet.microsoft.com/wiki/contents/articles/overview-of-microsoft-sql-azure-database.aspx?ocid=otc-f-corp-jtc-DPU-MVA_INTROSQLAZUREh
This article describes the data storage offerings available on the Windows Azure platform.
The following topics are discussed in this article:
Comparing
Windows Server and Windows Azure Data Storage
What
is Different About Data Storage on Windows Azure
Windows
Azure Platform Storage Offerings
Local
Storage
Windows
Azure Storage
Blob
Queue
Storage
Table
Storage
SQL
Azure Database
See
Also
References
If you are familiar with developing applications in a Windows Server environment, the data storage options available on the Windows Azure platform can be readily mapped to concepts that you are probably already familiar with. Some things, such as creating or
accessing a database in SQL Azure, are nearly identical to the Windows Server environment, while others will require different access methods.
Probably the most familiar storage offerings on the Windows Azure platform are SQL Azure and Windows Azure Queue storage. SQL
Azure is, essentially, SQL Server on the Azure platform; you can access it using the same access methods and tools that you would use with SQL Server. For the purposes of this article, we will only discuss the basic database storage functionality.
Windows Azure Queue storage
will be familiar to those of you who have used Microsoft Message Queue (MSMQ,) as it serves a similar purpose; durable storage for passing messages between processes.
If you’ve ever worked with a distributed application, or a clustered application, you’ve probably encountered the need for a durable, highly available, shared storage location. The most common
solution in a Windows Server environment is a network file share. This could be a cluster of dedicated file servers, a Distributed File System (DFS,) or Network Attached Storage (NAS,) but as far as your application is concerned it’s just a path to the file
resource that the application stores data on. The Windows Azure platform offers two specialized storage options that fill this purpose; Windows Azure Blob and Table storage.
For the storage of temporary data on a per instance basis, Windows Azure offers local
storage. This provides fast access to the physical storage on the hardware node that your application instance is running on; however it is not durable storage. If an application instance is stopped and then restarted
on a different hardware node, data stored in local storage does not follow the application instance.
Back to Top
When you move to the Windows Azure platform, there are some important differences between the Windows Azure platform and a Windows Server environment that you need to plan for:
While you can use normal .NET file IO classes with local storage, and ODBC or ADO.NET with SQL Azure, both Blob and Table storage require different access methods than you may be familiar with from a Windows Server environment
background.
Your application must gracefully handle failures when it loses a connection to data storage. Data storage instances or SQL Azure servers need to be stopped and restarted on
other hardware nodes for maintenance purposes, hardware may fail, etc. Applications written for the Windows Azure platform need to implement retry logic that allows them
to handle such occurences gracefully.
Your data store or SQL Azure server may be sharing a hardware node with someone else's data or SQL Azure server; don't assume that you have unlimited bandwidth or processing usage when accessing your data or running stored
procedures. Consider designing your data to be scaled out, or cache it in local storage for faster access.
You have to pay monthly for the storage you use, and some storage options cost extra when accessed from outside the Windows Azure platform or when accessed over a certain number of times. Allocate only what you need to use and
consider batching IO requests or caching data and periodically refreshing the cache with a worker process.
The bottom line is that the Windows Azure is a fully distributed platform that calls for new storage offerings to meet the needs of distributed applications, as well as new thinking about how data is accessed and used.
Back to Top
There are three main storage offerings on the Windows Azure platform, one of which (Windows Azure Storage,) is subdivided into more granular storage options:
All of the storage offerings except local storage and Azure Drive are accessible from both inside and outside the Windows Azure Platform. Local storage and Azure Drive are only accessible from applications running on Windows Azure.
Back to Top
Local storage is provided as part of the Windows Azure Compute offering, and provides temporary storage for a running application instance. Local storage represents a directory on the physical file system of the underlying hardware that an application instance
is running on, and can be used to store any information that is specific to the local running application instance. Since a local store is a directory on the local file system, you can use standard .NET file IO with it.
A local store is only accessible by the local instance, and can be configured to persist when the Web or Worker Role the instance runs in is recycled; however this only applies to a simple recycle of the role. If the instance
is restarted on different hardware, such as in the case of hardware failure or hardware maintenance, data in the local store will not follow the instance even if it was configured to persist through a recycle. If you require
reliable durability of your data, want to share data between instances, or access your data outside of Windows Azure, consider using a Windows Azure Storage account or SQL Azure Database instead.
You can create a number of local stores for each instance, with a default size for each store is 1mb. The store size can be increased to the maximum allowed by your compute instance. The maximum disk space for a compute instance depends on the VM size selected
for your instance, and is listed in the following table:
For more information on local storage, see:
Configuring Local Storage Resources
(http://msdn.microsoft.com/en-us/library/ee758708.aspx)
Back to Top
Blobs, Tables, and Queues are all available as part of the Windows Azure Storage account, and provide durable storage on the Windows Azure platform. All are accessible from both inside and outside the Windows Azure platform by using
classes in the Windows
Azure Storage Client SDK
(http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.storageclient.aspx,)
or via URI using REST
APIs
(http://msdn.microsoft.com/en-us/library/dd179355.aspx.)
Windows Azure Table Storage also supports LINQ access.
Unlike local storage, blobs, tables, and queues are accessible by multiple applications or application instances simultaneously, and represent dedicated storage instead of temporary.
See Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
for latest pricing information on Windows Azure Storage.
Back to Top
Blobs provide a way to store large amounts of unstructured, binary data, such as video, audio, images, etc. In fact, one of the features of blobs is streaming content such as video or audio.
There are two types of blob storage available, each provides specific functionality:
Block Blob
Optimized for streaming (upload and download)
Composed of blocks up to 4MB (largest block that can be submitted in one operation)
Blocks referenced by a unique Block ID
Allows blocks to be uploaded before being committed
Maximum size of 200GB (50,000 blocks)
Page Blob
Optimized for random access
Composed of pages that are referenced by offsets from the beginning of the blob
Maximum size of 1TB, which can be composed of multiple pages, or a single 1TB page
Blob storage provides options for storing metadata for each blob and for taking snapshots of blobs for backups. Blobs can also leverage the Content Delivery Network (CDN,)
which can be used to cache blobs at a datacenter located near your customers to ensure fast access to the data stored in the blob.
Blob storage can also be used to provide an NTFS file system to applications on the Windows Azure platform. This is called an Azure Drive, and is implemented as a page blob, which contains
an NTFS Virtual Hard Drive. This VHD is mounted and exposed as a local drive letter (e.g. X:\,) to the application. The Azure Drive VHD is only available in Windows Azure Guest OS 1.1 or later, and is only
mountable by an application hosted within Windows Azure.
For more information on blob storage, see:
Understanding Block Blobs and Page Blobs
(http://msdn.microsoft.com/en-us/library/ee691964.aspx)
Blob Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179376.aspx)
Windows Azure Storage Services REST API Reference
(http://msdn.microsoft.com/en-us/library/dd179355.aspx)
Delivering High-Bandwidth Content with the Windows Azure
CDN
(http://msdn.microsoft.com/en-us/library/ee795176.aspx
)
Windows Azure Drives white paper
(http://go.microsoft.com/?linkid=9710117)
Back to Top
Queues provide storage for passing messages between applications, similar to Microsoft Message Queuing (MSMQ.) Messages stored to the queue are limited to a maximum of 8KB in size, and are
generally stored and retrieved on a first in, first out (FIFO,) basis; however FIFO is not guaranteed.
Processing messages from a queue is a two stage process, which involves getting the message, and then deleting the
message after it has been processed. This pattern allows you to implement guaranteed message delivery by leaving the message in the queue until it has been fully processed. If the application processing the message
fails before it has completed processing, the message is left in the queue and can be processed by another application. To prevent the message from being processed by multiple applications simultaneously, Getting the message cause it to be marked as invisible
when it is first read and remains invisible until it is either deleted or a specified time interval has passed. Peeking the message reads the message but does not mark it as invisible.
For more information on queue storage, see:
Queue Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179353.aspx)
Queue Service API
(http://msdn.microsoft.com/en-us/library/dd179363.aspx)
Back to Top
Table storage is a collection of row like entities, each of which can contain up to 255 properties; however unlike tables in a database, there is no schema
that enforces a certain set of values on all the rows within a table. And while a table stores structured data, it does not provide any way to represent relationships between data. Windows
Azure Storage tables are more like rows within a spreadsheet application such as Excel than rows within a database such as SQL Azure, in that each row can contain a different number of columns, and of different data types, than the other rows in the same table.
While table storage does support basic operations such as insert, update, delete, and select, it does not support joins, foreign keys, stored procedures, triggers, or any processing on the storage engine side, such as SQL Azure does. Queries
returning a large number of results, or queries that time out, return partial results along with a continuation token that allows the query to be resumed.
A table can be up to 100TB in size, and each row entity within a table can be up to 1MB in size. Each
row entity can contain up to 255 properties (columns,) of which 3 are always a partition key that uniquely
identifies the table, a row key that uniquely identifies the row entity within the table, a timestamp. Partition and row keys are limited to 1KBin size, and
represent the only index that exists on data within the table. Tables are partitioned based on the partition key for load balancing or scale out, as each partition can be located on a different storage node on the Windows
Azure platform.
Properties within a row entity are name value pairs that conform to a subset of the data types defined by theADO.NET
Data Services
specification.
The following table shows the supported types:
For more information on table storage, see:
Understanding the Table Storage Data Model
(http://msdn.microsoft.com/en-us/library/dd179338.aspx)
Table Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179463.aspx)
Querying Tables and Entities
(http://msdn.microsoft.com/en-us/library/dd894031.aspx)
Back to Top
SQL Azure provides a Relational Database Management System for the Windows Azure platform, and is based on SQL Server technology. Similar to SQL Server, SQL
Azure exposes a tabular data stream (TDS) interface, and Transact-SQL (T-SQL, so many of the tools and applications that work with SQL Server also work with SQL Azure. Applications written using existing technologies
such as ADO.NET and ODBC that communicate with SQL Server can be used to access SQL Azure databases with minimal code changes. SQL Azure also provides standard SQL Server features such as stored procedures, views, multiple
indices, joins, aggregation, etc.
Since the Windows Azure platform does not provide direct access to the underlying hardware, administration tasks that involve hardware access, such as defining where the database file is located, are inaccessible in SQL Azure.
Physical administration tasks are handled automatically by the platform, though you must still perform logical administration tasks such as creating logins, users, roles, etc. Because you cannot directly access the hardware, there
are some differences between SQL Server and SQL Azure in terms of administration, provisioning, T-SQL support, programming model and features. For more information, see General
Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx.)
Unlike the other storage offerings discussed so-far, SQL Azure provides more than simple data storage; it also provides server side processing, which allows you to perform complex processing on stored data without having to retrieve and process the entire data
set within your application. For example, a query to find all salesmen with sales greater than $1,000.00 in the past year, within a specific region of the country, and provide a sum total of all their sales, can be ran completely by SQL Server and the results
returned to your application.
A SQL Azure database can be up to 50GB in size and can contain multiple tables with complex relationships between data in the tables. Rows can be up to 8MB in size, and can contain 1024 columns.
A table within SQL Azure can have one clustered index on any column, and up to 999 secondary indexes.
See Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
for latest pricing information on SQL Azure.
For more information on SQL Azure, see:
Introducing SQL Azure Database
(http://msdn.microsoft.com/en-us/library/ee336230.aspx)
SQL Azure Database Concepts
(http://msdn.microsoft.com/en-us/library/ee336256.aspx)
Transact-SQL Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336250.aspx)
SQL Server Tools and Utilities Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee621784.aspx)
General Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx)
SQL Azure Survival Guide (http://social.technet.microsoft.com/wiki/contents/articles/sql-azure-survival-guide.aspx)
Back to Top
Comparing
SQL Server with SQL Azure
SQL
Azure TechNet Wiki Articles Index
Back to Top
Configuring Local Storage Resources
(http://msdn.microsoft.com/en-us/library/ee758708.aspx)
Understanding Block Blobs and Page Blobs
(http://msdn.microsoft.com/en-us/library/ee691964.aspx)
Blob Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179376.aspx)
Windows Azure Storage Services REST API Reference
(http://msdn.microsoft.com/en-us/library/dd179355.aspx)
Windows Azure Drives white paper
(http://go.microsoft.com/?linkid=9710117)
Queue Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179353.aspx)
Queue Service API
(http://msdn.microsoft.com/en-us/library/dd179363.aspx)
Understanding the Table Storage Data Model
(http://msdn.microsoft.com/en-us/library/dd179338.aspx)
Table Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179463.aspx)
Introducing SQL Azure Database
(http://msdn.microsoft.com/en-us/library/ee336230.aspx)
SQL Azure Database Concepts
(http://msdn.microsoft.com/en-us/library/ee336256.aspx)
Transact-SQL Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336250.aspx)
SQL Server Tools and Utilities Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee621784.aspx)
General Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx)
SQL Azure Survival Guide (http://social.technet.microsoft.com/wiki/contents/articles/sql-azure-survival-guide.aspx)
Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
Overview
of Options for Migrating Data and Schema to SQL Azure(http://social.technet.microsoft.com/wiki/contents/articles/overview-of-options-for-migrating-data-and-schema-to-sql-azure.aspx)
Querying Tables and Entities
(http://msdn.microsoft.com/en-us/library/dd894031.aspx)
Data Types (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336233.aspx)
Handling Transactions in SQL
Azure(http://social.technet.microsoft.com/wiki/contents/articles/handling-transactions-in-sql-azure.aspx)
Windows Azure Storage Client
SDK
(http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.storageclient.aspx)
Back to Top
This article describes the data storage offerings available on the Windows Azure platform.
 Note |
|---|
| If you wish to contribute to this page, use the Edit tab at the top (sign-in required). If you wish to provide feedback for this documentation please either send e-mail to azuredocs@microsoft.com or use the Comment field at the bottom of this page (sign-in required). |
Comparing
Windows Server and Windows Azure Data Storage
What
is Different About Data Storage on Windows Azure
Windows
Azure Platform Storage Offerings
Local
Storage
Windows
Azure Storage
Blob
Queue
Storage
Table
Storage
SQL
Azure Database
See
Also
References
Comparing Windows Server and Windows Azure Data Storage
If you are familiar with developing applications in a Windows Server environment, the data storage options available on the Windows Azure platform can be readily mapped to concepts that you are probably already familiar with. Some things, such as creating oraccessing a database in SQL Azure, are nearly identical to the Windows Server environment, while others will require different access methods.
Probably the most familiar storage offerings on the Windows Azure platform are SQL Azure and Windows Azure Queue storage. SQL
Azure is, essentially, SQL Server on the Azure platform; you can access it using the same access methods and tools that you would use with SQL Server. For the purposes of this article, we will only discuss the basic database storage functionality.
Windows Azure Queue storage
will be familiar to those of you who have used Microsoft Message Queue (MSMQ,) as it serves a similar purpose; durable storage for passing messages between processes.
If you’ve ever worked with a distributed application, or a clustered application, you’ve probably encountered the need for a durable, highly available, shared storage location. The most common
solution in a Windows Server environment is a network file share. This could be a cluster of dedicated file servers, a Distributed File System (DFS,) or Network Attached Storage (NAS,) but as far as your application is concerned it’s just a path to the file
resource that the application stores data on. The Windows Azure platform offers two specialized storage options that fill this purpose; Windows Azure Blob and Table storage.
For the storage of temporary data on a per instance basis, Windows Azure offers local
storage. This provides fast access to the physical storage on the hardware node that your application instance is running on; however it is not durable storage. If an application instance is stopped and then restarted
on a different hardware node, data stored in local storage does not follow the application instance.
Back to Top
What is Different about Data Storage on Windows Azure
When you move to the Windows Azure platform, there are some important differences between the Windows Azure platform and a Windows Server environment that you need to plan for:While you can use normal .NET file IO classes with local storage, and ODBC or ADO.NET with SQL Azure, both Blob and Table storage require different access methods than you may be familiar with from a Windows Server environment
background.
Your application must gracefully handle failures when it loses a connection to data storage. Data storage instances or SQL Azure servers need to be stopped and restarted on
other hardware nodes for maintenance purposes, hardware may fail, etc. Applications written for the Windows Azure platform need to implement retry logic that allows them
to handle such occurences gracefully.
Your data store or SQL Azure server may be sharing a hardware node with someone else's data or SQL Azure server; don't assume that you have unlimited bandwidth or processing usage when accessing your data or running stored
procedures. Consider designing your data to be scaled out, or cache it in local storage for faster access.
You have to pay monthly for the storage you use, and some storage options cost extra when accessed from outside the Windows Azure platform or when accessed over a certain number of times. Allocate only what you need to use and
consider batching IO requests or caching data and periodically refreshing the cache with a worker process.
The bottom line is that the Windows Azure is a fully distributed platform that calls for new storage offerings to meet the needs of distributed applications, as well as new thinking about how data is accessed and used.
Back to Top
Windows Azure Platform Storage Offerings
There are three main storage offerings on the Windows Azure platform, one of which (Windows Azure Storage,) is subdivided into more granular storage options:| Storage Offering | Purpose | Maximum Size | Cost |
|---|---|---|---|
| Local Storage | Per-instance temporary storage | 250GB to 2TB | Included in Compute Account price. See Windows Azure Pricing (http://www.microsoft.com/windowsazure/pricing/) for latest pricing information on Compute accounts. |
| Windows Azure Storage | Durable storage for..... | See Windows Azure Pricing (http://www.microsoft.com/windowsazure/pricing/) for latest pricing information on Storage accounts. | |
| Blob | Large binary objects such as video or audio | 200GB or 1TB | |
| Table | Structured data | 100TB | |
| Queue | Inter-process Messages | 100TB | |
| SQL Azure Database | Relational Database Management System | 50GB | See Windows Azure Pricing (http://www.microsoft.com/windowsazure/pricing/) for latest pricing information on SQL Azure. |
Back to Top
Local Storage
Local storage is provided as part of the Windows Azure Compute offering, and provides temporary storage for a running application instance. Local storage represents a directory on the physical file system of the underlying hardware that an application instanceis running on, and can be used to store any information that is specific to the local running application instance. Since a local store is a directory on the local file system, you can use standard .NET file IO with it.
A local store is only accessible by the local instance, and can be configured to persist when the Web or Worker Role the instance runs in is recycled; however this only applies to a simple recycle of the role. If the instance
is restarted on different hardware, such as in the case of hardware failure or hardware maintenance, data in the local store will not follow the instance even if it was configured to persist through a recycle. If you require
reliable durability of your data, want to share data between instances, or access your data outside of Windows Azure, consider using a Windows Azure Storage account or SQL Azure Database instead.
You can create a number of local stores for each instance, with a default size for each store is 1mb. The store size can be increased to the maximum allowed by your compute instance. The maximum disk space for a compute instance depends on the VM size selected
for your instance, and is listed in the following table:
| VM Size | CPU Cores | Memory | Disk Space for Local Storage Resources |
|---|---|---|---|
| Small | 1 | 1.7 GB | 250 GB |
| Medium | 2 | 3.5 GB | 500 GB |
| Large | 4 | 7 GB | 1 TB |
| ExtraLarge | 8 | 14 GB | 2 TB |
Configuring Local Storage Resources
(http://msdn.microsoft.com/en-us/library/ee758708.aspx)
Back to Top
Windows Azure Storage
Blobs, Tables, and Queues are all available as part of the Windows Azure Storage account, and provide durable storage on the Windows Azure platform. All are accessible from both inside and outside the Windows Azure platform by usingclasses in the Windows
Azure Storage Client SDK
(http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.storageclient.aspx,)
or via URI using REST
APIs
(http://msdn.microsoft.com/en-us/library/dd179355.aspx.)
Windows Azure Table Storage also supports LINQ access.
Unlike local storage, blobs, tables, and queues are accessible by multiple applications or application instances simultaneously, and represent dedicated storage instead of temporary.
See Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
for latest pricing information on Windows Azure Storage.
Back to Top
Blob
Blobs provide a way to store large amounts of unstructured, binary data, such as video, audio, images, etc. In fact, one of the features of blobs is streaming content such as video or audio.There are two types of blob storage available, each provides specific functionality:
Block Blob
Optimized for streaming (upload and download)
Composed of blocks up to 4MB (largest block that can be submitted in one operation)
Blocks referenced by a unique Block ID
Allows blocks to be uploaded before being committed
Maximum size of 200GB (50,000 blocks)
Page Blob
Optimized for random access
Composed of pages that are referenced by offsets from the beginning of the blob
Maximum size of 1TB, which can be composed of multiple pages, or a single 1TB page
Blob storage provides options for storing metadata for each blob and for taking snapshots of blobs for backups. Blobs can also leverage the Content Delivery Network (CDN,)
which can be used to cache blobs at a datacenter located near your customers to ensure fast access to the data stored in the blob.
Blob storage can also be used to provide an NTFS file system to applications on the Windows Azure platform. This is called an Azure Drive, and is implemented as a page blob, which contains
an NTFS Virtual Hard Drive. This VHD is mounted and exposed as a local drive letter (e.g. X:\,) to the application. The Azure Drive VHD is only available in Windows Azure Guest OS 1.1 or later, and is only
mountable by an application hosted within Windows Azure.
For more information on blob storage, see:
Understanding Block Blobs and Page Blobs
(http://msdn.microsoft.com/en-us/library/ee691964.aspx)
Blob Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179376.aspx)
Windows Azure Storage Services REST API Reference
(http://msdn.microsoft.com/en-us/library/dd179355.aspx)
Delivering High-Bandwidth Content with the Windows Azure
CDN
(http://msdn.microsoft.com/en-us/library/ee795176.aspx
)
Windows Azure Drives white paper
(http://go.microsoft.com/?linkid=9710117)
Back to Top
Queue Storage
Queues provide storage for passing messages between applications, similar to Microsoft Message Queuing (MSMQ.) Messages stored to the queue are limited to a maximum of 8KB in size, and aregenerally stored and retrieved on a first in, first out (FIFO,) basis; however FIFO is not guaranteed.
Processing messages from a queue is a two stage process, which involves getting the message, and then deleting the
message after it has been processed. This pattern allows you to implement guaranteed message delivery by leaving the message in the queue until it has been fully processed. If the application processing the message
fails before it has completed processing, the message is left in the queue and can be processed by another application. To prevent the message from being processed by multiple applications simultaneously, Getting the message cause it to be marked as invisible
when it is first read and remains invisible until it is either deleted or a specified time interval has passed. Peeking the message reads the message but does not mark it as invisible.
For more information on queue storage, see:
Queue Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179353.aspx)
Queue Service API
(http://msdn.microsoft.com/en-us/library/dd179363.aspx)
Back to Top
Table Storage
Table storage is a collection of row like entities, each of which can contain up to 255 properties; however unlike tables in a database, there is no schemathat enforces a certain set of values on all the rows within a table. And while a table stores structured data, it does not provide any way to represent relationships between data. Windows
Azure Storage tables are more like rows within a spreadsheet application such as Excel than rows within a database such as SQL Azure, in that each row can contain a different number of columns, and of different data types, than the other rows in the same table.
While table storage does support basic operations such as insert, update, delete, and select, it does not support joins, foreign keys, stored procedures, triggers, or any processing on the storage engine side, such as SQL Azure does. Queries
returning a large number of results, or queries that time out, return partial results along with a continuation token that allows the query to be resumed.
A table can be up to 100TB in size, and each row entity within a table can be up to 1MB in size. Each
row entity can contain up to 255 properties (columns,) of which 3 are always a partition key that uniquely
identifies the table, a row key that uniquely identifies the row entity within the table, a timestamp. Partition and row keys are limited to 1KBin size, and
represent the only index that exists on data within the table. Tables are partitioned based on the partition key for load balancing or scale out, as each partition can be located on a different storage node on the Windows
Azure platform.
Properties within a row entity are name value pairs that conform to a subset of the data types defined by theADO.NET
Data Services
specification.
The following table shows the supported types:
| ADO.NET Data Services type | Common Language Runtime type | Details |
|---|---|---|
| Edm.Binary | byte[] | An array of bytes up to 64 KB in size. |
| Edm.Boolean | bool | A Boolean value. |
| Edm.DateTime | DateTime | A 64-bit value expressed as Coordinated Universal Time (UTC). The supportedDateTime range begins from 12:00 midnight, January 1, 1601 A.D. (C.E.), UTC. The range ends at December 31, 9999. |
| Edm.Double | double | A 64-bit floating point value. |
| Edm.Guid | Guid | A 128-bit globally unique identifier. |
| Edm.Int32 | Int32 or int | A 32-bit integer. |
| Edm.Int64 | Int64 or long | A 64-bit integer. |
| Edm.String | String | A UTF-16-encoded value. String values may be up to 64 KB in size. |
Understanding the Table Storage Data Model
(http://msdn.microsoft.com/en-us/library/dd179338.aspx)
Table Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179463.aspx)
Querying Tables and Entities
(http://msdn.microsoft.com/en-us/library/dd894031.aspx)
Back to Top
SQL Azure Database
SQL Azure provides a Relational Database Management System for the Windows Azure platform, and is based on SQL Server technology. Similar to SQL Server, SQLAzure exposes a tabular data stream (TDS) interface, and Transact-SQL (T-SQL, so many of the tools and applications that work with SQL Server also work with SQL Azure. Applications written using existing technologies
such as ADO.NET and ODBC that communicate with SQL Server can be used to access SQL Azure databases with minimal code changes. SQL Azure also provides standard SQL Server features such as stored procedures, views, multiple
indices, joins, aggregation, etc.
Since the Windows Azure platform does not provide direct access to the underlying hardware, administration tasks that involve hardware access, such as defining where the database file is located, are inaccessible in SQL Azure.
Physical administration tasks are handled automatically by the platform, though you must still perform logical administration tasks such as creating logins, users, roles, etc. Because you cannot directly access the hardware, there
are some differences between SQL Server and SQL Azure in terms of administration, provisioning, T-SQL support, programming model and features. For more information, see General
Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx.)
Unlike the other storage offerings discussed so-far, SQL Azure provides more than simple data storage; it also provides server side processing, which allows you to perform complex processing on stored data without having to retrieve and process the entire data
set within your application. For example, a query to find all salesmen with sales greater than $1,000.00 in the past year, within a specific region of the country, and provide a sum total of all their sales, can be ran completely by SQL Server and the results
returned to your application.
A SQL Azure database can be up to 50GB in size and can contain multiple tables with complex relationships between data in the tables. Rows can be up to 8MB in size, and can contain 1024 columns.
A table within SQL Azure can have one clustered index on any column, and up to 999 secondary indexes.
See Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
for latest pricing information on SQL Azure.
For more information on SQL Azure, see:
Introducing SQL Azure Database
(http://msdn.microsoft.com/en-us/library/ee336230.aspx)
SQL Azure Database Concepts
(http://msdn.microsoft.com/en-us/library/ee336256.aspx)
Transact-SQL Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336250.aspx)
SQL Server Tools and Utilities Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee621784.aspx)
General Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx)
SQL Azure Survival Guide (http://social.technet.microsoft.com/wiki/contents/articles/sql-azure-survival-guide.aspx)
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See Also
ComparingSQL Server with SQL Azure
SQL
Azure TechNet Wiki Articles Index
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References
Configuring Local Storage Resources(http://msdn.microsoft.com/en-us/library/ee758708.aspx)
Understanding Block Blobs and Page Blobs
(http://msdn.microsoft.com/en-us/library/ee691964.aspx)
Blob Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179376.aspx)
Windows Azure Storage Services REST API Reference
(http://msdn.microsoft.com/en-us/library/dd179355.aspx)
Windows Azure Drives white paper
(http://go.microsoft.com/?linkid=9710117)
Queue Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179353.aspx)
Queue Service API
(http://msdn.microsoft.com/en-us/library/dd179363.aspx)
Understanding the Table Storage Data Model
(http://msdn.microsoft.com/en-us/library/dd179338.aspx)
Table Service Concepts
(http://msdn.microsoft.com/en-us/library/dd179463.aspx)
Introducing SQL Azure Database
(http://msdn.microsoft.com/en-us/library/ee336230.aspx)
SQL Azure Database Concepts
(http://msdn.microsoft.com/en-us/library/ee336256.aspx)
Transact-SQL Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336250.aspx)
SQL Server Tools and Utilities Support (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee621784.aspx)
General Guidelines and Limitations (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336245.aspx)
SQL Azure Survival Guide (http://social.technet.microsoft.com/wiki/contents/articles/sql-azure-survival-guide.aspx)
Windows Azure Pricing
(http://www.microsoft.com/windowsazure/pricing/)
Overview
of Options for Migrating Data and Schema to SQL Azure(http://social.technet.microsoft.com/wiki/contents/articles/overview-of-options-for-migrating-data-and-schema-to-sql-azure.aspx)
Querying Tables and Entities
(http://msdn.microsoft.com/en-us/library/dd894031.aspx)
Data Types (SQL Azure Database)
(http://msdn.microsoft.com/en-us/library/ee336233.aspx)
Handling Transactions in SQL
Azure(http://social.technet.microsoft.com/wiki/contents/articles/handling-transactions-in-sql-azure.aspx)
Windows Azure Storage Client
SDK
(http://msdn.microsoft.com/en-us/library/microsoft.windowsazure.storageclient.aspx)
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