Copying an Azure Blob snapshot to another storage account using PowerShell

I've been working with Azure Blobs and Snapshots recently. One gripe is that the Azure portal and the various storage explorers don't give you the power to copy a blob snapshot. Blobs, yes, but their snapshots, no.

Depending on your requirements there are many approaches. The PowerShell below gives an example where the snapshot timestamp is extracted from the snapshot URI and then used to obtain an object to the specific snapshot before copying it with the Start-AzureStorageBlobCopy cmdlet.

# Define the source snapshot blob URI
$SrcBlobURI="https://<SOURCE_STORAGE_ACCOUNT>.blob.core.windows.net/vhds/<SOURCE_VHD_PREFIX>.vhd?snapshot=2017-01-24T21:08:36.9371576Z"

# Define the destination storage account and context.
$DestStorageAccountName = "<DESTINATION_STORAGE_ACCOUNT>"
$DestStorageAccountKey = "<DESTINATION_STORAGE_ACCOUNT_KEY>"
$DestContainerName = "<DESTINATION_CONTAINER_NAME>"
$DestContext = New-AzureStorageContext -StorageAccountName $DestStorageAccountName -StorageAccountKey $DestStorageAccountKey

# Determine source snapshot blob container name and context
$SrcDiskInfo = "" | Select StorageAccountName, VHDName, ContainerName
$SrcDiskInfo.StorageAccountName = ($SrcBlobURI -split "https://")[1].Split(".")[0]
$SrcDiskInfo.VHDName = $SrcBlobURI.Split("/")[-1]
$SrcDiskInfo.ContainerName = $SrcBlobURI.Split("/")[3]
$SrcContainerName = $SrcDiskInfo.ContainerName
$SrcStorageAccount = Find-AzureRmResource `
    -ResourceNameContains $SrcDiskInfo.StorageAccountName `
    -WarningAction Ignore
$SrcStorageKey = Get-AzureRmStorageAccountKey `
    -Name $SrcStorageAccount.Name `
    -ResourceGroupName $SrcStorageAccount.ResourceGroupName
$SrcContext = New-AzureStorageContext `
    -StorageAccountName $SrcStorageAccount.Name `
    -StorageAccountKey $SrcStorageKey[0].Value

# Extract timestamp from the Snapshot filename and convert to a datetime
$pre, $post = $SrcBlobURI.split("=")
$snapdt = [uri]::UnescapeDataString($post)
$snapdt = [datetime]::ParseExact( `
    $snapdt,'yyyy-MM-dd"T"HH:mm:ss"."fffffff"Z"',$null `
)

# Get a reference to blobs in the source container.
$blob = Get-AzureStorageBlob -Container $SrcContainerName `
    -Context $SrcContext `
    | Where-Object {`
        $_.ICloudBlob.IsSnapshot `
        -and $_.SnapshotTime -eq $snapdt `
    }

# Copy blobs from one container to another.
$blob | Start-AzureStorageBlobCopy `
    -DestContainer $DestContainerName `
    -DestContext $DestContext `
    -DestBlob "acopy_$($blob.Name)"

Azure Premium Storage Blob Snapshot Error - 409 Conflict

I've recently been working in more detail with Azure blob snapshots and (by trial and error) discovered that Premium storage imposes limitations on the number and frequency of snapshots that can be performed on a single blob.

If you create a snapshot of a Premium storage blob and then another in quick succession (within 60 seconds of each other), then you might get a 409/Conflict error message.

This article suggests that there are two possibilities for this error, either

• SnapshotCountExceeded - You've exceeded the limit of 100 snapshots per blob, or
• SnaphotOperationRateExceeded - You've exceeded the limit of snapshots within a time window (stated as 10 minutes, but I observed this as closer to 1 minute)

Whilst it's unlikely that these limits would cause a problem in practice, it's something to keep in mind when developing/testing solutions that make use of the blob snapshot facility.