/// <summary>
/// Demonstrates how to do backup using incremental snapshots. See this article on
/// backing up Azure virtual machine disks with incremental snapshots:
/// https://azure.microsoft.com/en-us/documentation/articles/storage-incremental-snapshots/
/// The article also describes how to restore a disk from incremental snapshots.
/// </summary>
/// <returns>Task</returns>
public static async Task IncrementalSnapshotBackupAsync()
{
const int TotalBlobSize = 512 * 6; // The total amount of data in the blob
const int UpdateWriteSize = 512 * 2; // The amount of data to update in the blob
const int UpdateWriteOffset = 512 * 2; // The offset at which to write updated data
const int ClearPagesOffset = 512 * 5; // The offset at which to begin clearing page data
const int ClearPagesSize = 512; // The amount of data to clear in the blob
string SimulationID = Guid.NewGuid().ToString(); // The simulation ID
string ContainerName = "container-" + SimulationID; // The name of the primary container
string PageBlobName = "binary-data"; // The name of the primary page blob
// Retrieve storage account information from connection strings
// How to create storage connection strings - http://msdn.microsoft.com/en-us/library/azure/ee758697.aspx
CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
CloudConfigurationManager.GetSetting("StorageConnectionString"));
CloudStorageAccount backupStorageAccount = CloudStorageAccount.Parse(
CloudConfigurationManager.GetSetting("BackupStorageConnectionString"));
// Create blob clients for interacting with the blob service.
CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
CloudBlobClient backupBlobClient = backupStorageAccount.CreateCloudBlobClient();
// Create containers for organizing blobs within the storage accounts.
container = blobClient.GetContainerReference(ContainerName);
backupContainer = backupBlobClient.GetContainerReference("copy-of-" + ContainerName);
try
{
// The call below will fail if the sample is configured to use the storage emulator
// in the connection string, but the emulator is not running.
BlobRequestOptions requestOptions = new BlobRequestOptions()
{
RetryPolicy = new NoRetry()
};
await container.CreateIfNotExistsAsync(requestOptions, null);
await backupContainer.CreateIfNotExistsAsync(requestOptions, null);
}
catch (StorageException)
{
Console.WriteLine("If you are running with the default connection string, please make " +
"sure you have started the storage emulator. Press the Windows key and type Azure " +
"Storage to select and run it from the list of applications - then restart the sample.");
Console.ReadLine();
throw;
}
// Create, write to, and snapshot a page blob in the newly created container.
CloudPageBlob pageBlob = container.GetPageBlobReference(PageBlobName);
await pageBlob.CreateAsync(TotalBlobSize);
byte[] samplePagedata = new byte[TotalBlobSize];
Random random = new Random();
random.NextBytes(samplePagedata);
await pageBlob.UploadFromByteArrayAsync(samplePagedata, 0, samplePagedata.Length);
CloudPageBlob pageBlobSnap = await pageBlob.CreateSnapshotAsync();
// Create a blob in the backup account
CloudPageBlob pageBlobBackup = backupContainer.GetPageBlobReference("copy-of-" + PageBlobName);
// Copy to the blob in the backup account. Notice that the <isServiceCopy> flag here is
// set to 'false'. This forces data to be first downloaded from the source, then uploaded
// to the destination. If <isServiceCopy> were set to 'true' we could avoid the I/O of
// downloading and then uploading, but could not guarantee that the copy completed even
// after the local task completed. Since the remainder of this sample depends on the
// successful completion of this operation, we must set <isServiceCopy> to 'false.'
await TransferManager.CopyAsync(pageBlobSnap, pageBlobBackup, false);
// Snapshot the backup copy
CloudPageBlob pageBlobBackupSnap = await pageBlob.CreateSnapshotAsync();
// Change the contents of the original page blob (note: we must convert the byte array to a
// stream in order to write to a non-zero offset in the page blob) and snapshot.
byte[] updatePageData = new byte[UpdateWriteSize];
random.NextBytes(updatePageData);
Stream updatePageDataStream = new MemoryStream(updatePageData);
await pageBlob.WritePagesAsync(updatePageDataStream, UpdateWriteOffset, null);
await pageBlob.ClearPagesAsync(ClearPagesOffset, ClearPagesSize);
CloudPageBlob newPageBlobSnap = await pageBlob.CreateSnapshotAsync();
// Get the incremental changes and write to the backup.
IEnumerable <PageDiffRange> changedPages =
await newPageBlobSnap.GetPageRangesDiffAsync(pageBlobSnap.SnapshotTime.Value);
foreach (PageDiffRange pageRange in changedPages)
{
// If this page range is cleared, remove the old data in the backup.
if (pageRange.IsClearedPageRange)
{
await pageBlobBackup.ClearPagesAsync(
pageRange.StartOffset, pageRange.EndOffset - pageRange.StartOffset + 1);
}
// If this page range is not cleared, write the new data to the backup.
else
{
byte[] toWrite = new byte[pageRange.EndOffset - pageRange.StartOffset + 1];
await newPageBlobSnap.DownloadRangeToByteArrayAsync(
toWrite, 0, pageRange.StartOffset, pageRange.EndOffset - pageRange.StartOffset + 1);
Stream toWriteStream = new MemoryStream(toWrite);
await pageBlobBackup.WritePagesAsync(toWriteStream, pageRange.StartOffset, null);
}
}
// Snapshot the backup blob and delete the old snapshot from the primary account
CloudPageBlob pageBlobBackupSnapv2 = await pageBlobBackup.CreateSnapshotAsync();
await pageBlobSnap.DeleteAsync();
}
