Benchmarking Azure VM storage

Azure Standard tier virtual machines come with an optional number of persistent page blob disks, up to 1 terabyte each. These disks are expected to deliver 500 IOPS or 60 MB/s throughput each. 

Let’s see if we can make that happen.

I started by creating a new Standard Storage account. This is to make sure I’m not hitting the limitation of 20k IOPS/Standard Storage account during testing.

I created a new Standard A3 VM.

From my on-premises management machine, I used Powershell to create and attach 8x 1TB disks to the VM. To get started with Powershell for Azure see this post.

# Input
$SubscriptionName = '###Removed###' 
$StorageAccount = 'testdisks1storageaccount'
$VMName = 'testdisks1vm'
$ServiceName = 'testdisks1cloudservice'
$PwdFile = ".\$VMName-###Removed###.txt"
$AdminName = '###Removed###'

# Initialize
Set-AzureSubscription -SubscriptionName $SubscriptionName -CurrentStorageAccount $StorageAccount
$objVM = Get-AzureVM -Name $VMName -ServiceName $ServiceName
$VMFQDN = (Get-AzureWinRMUri -ServiceName $ServiceName).Host
$Port = (Get-AzureWinRMUri -ServiceName $ServiceName).Port

# Create and attach 8x 1TB disks
0..7 | % { $_
  $objVM | Add-AzureDataDisk -CreateNew -DiskSizeInGB 1023 -DiskLabel "Disk$_" -LUN $_ | Update-AzureVM
}

Next I used Powershell remoting to create a Storage Space optimized for 1 MB writes. The intend is to use the VM with Veeam Cloud Connect. This particular workloads uses 1 MB write operations.

This code block connects to the Azure VM:

# Remote to the VM 
# Get certificate for Powershell remoting to the Azure VM if not installed already
Write-Verbose "Adding certificate 'CN=$VMFQDN' to 'LocalMachine\Root' certificate store.." 
$Thumbprint = (Get-AzureVM -ServiceName $ServiceName -Name $VMName | 
  select -ExpandProperty VM).DefaultWinRMCertificateThumbprint
$Temp = [IO.Path]::GetTempFileName()
(Get-AzureCertificate -ServiceName $ServiceName -Thumbprint $Thumbprint -ThumbprintAlgorithm sha1).Data | Out-File $Temp
$Cert = New-Object System.Security.Cryptography.X509Certificates.X509Certificate2 $Temp
$store = New-Object System.Security.Cryptography.X509Certificates.X509Store "Root","LocalMachine"
$store.Open([System.Security.Cryptography.X509Certificates.OpenFlags]::ReadWrite)
$store.Add($Cert)
$store.Close()
Remove-Item $Temp -Force -Confirm:$false

# Attempt to open Powershell session to Azure VM
Write-Verbose "Opening PS session with computer '$VMName'.." 
if (-not (Test-Path -Path $PwdFile)) { 
  Write-Verbose "Pwd file '$PwdFile' not found, prompting to pwd.."
  Read-Host "Enter the pwd for '$AdminName' on '$VMFQDN'" -AsSecureString | 
    ConvertFrom-SecureString | Out-File $PwdFile 
}
$Pwd = Get-Content $PwdFile | ConvertTo-SecureString 
$Cred = New-Object -TypeName System.Management.Automation.PSCredential -ArgumentList $AdminName, $Pwd
$Session = New-PSSession -ComputerName $VMFQDN -Port $Port -UseSSL -Credential $Cred -ErrorAction Stop

Now I have an open PS session with the Azure VM and can execute commands and get output back.

Next I check/verify available disks on the VM:

$ScriptBlock = { Get-PhysicalDisk -CanPool $True }
$Result = Invoke-Command -Session $Session -ScriptBlock $ScriptBlock 
$Result | sort friendlyname | FT -a 

Then I create an 8-column simple storage space optimized for 1 MB stripe size:

$ScriptBlock = { 
  $PoolName = "VeeamPool3"
  $vDiskName = "VeeamVDisk3"
  $VolumeLabel = "VeeamRepo3"
  New-StoragePool -FriendlyName $PoolName -StorageSubsystemFriendlyName “Storage Spaces*” -PhysicalDisks (Get-PhysicalDisk -CanPool $True) |
    New-VirtualDisk -FriendlyName $vDiskName -UseMaximumSize -ProvisioningType Fixed -ResiliencySettingName Simple -NumberOfColumns 16 -Interleave 64KB |
      Initialize-Disk -PassThru -PartitionStyle GPT |
        New-Partition -AssignDriveLetter -UseMaximumSize | 
          Format-Volume -FileSystem NTFS -NewFileSystemLabel $VolumeLabel -AllocationUnitSize 64KB -Confirm:$false
  Get-VirtualDisk | select FriendlyName,Interleave,LogicalSectorSize,NumberOfColumns,PhysicalSectorSize,ProvisioningType,ResiliencySettingName,Size,WriteCacheSize
}
$Result = Invoke-Command -Session $Session -ScriptBlock $ScriptBlock 
$Result | FT -a 

Next I RDP to the VM, and run IOMeter using the following settings:

• All 4 workers (CPU cores)
• Maximum Disk Size 1,024,000 sectors (512 MB test file)
• # of Outstanding IOs: 20 per target. This is make sure the target disk is getting plenty of requests during the test
• Access specification: 64KB, 50% read, 50% write

I’m expecting to see 4K IOPS and 320 MB/s throughput. (8 disks x 500 IOPS or 60 MB/s each). But this is what I get:

I got about 1.3 K IOPS instead of 4K, and about 90 MB/s throughput instead of 480 MB/s.

This VM and storage account are in East US 2 region.

This is consistent with other people’s findings like this post.

I also tested using the same 8 disks as a striped disk in Windows. I removed the volume, vDisk, Storage Space, then provisioned a traditional RAID 0 striped disk in this Windows Server 2012 R2 VM. Results were slightly better:

This is still far off the expected 4k IOPS or 480 MB/s I should be seeing here.

I upgraded the VM to Standard A4 tier, and repeated the same tests:

Standard A4 VM can have a maximum of 16x 1TB persistent page blob disks. I used powershell to provision and attach 16 disks. Then create a storage space with 16 columns optimized for 1 MB stripe:

Then I benchmarked storage performance on drive e: using same exact IOMeter settings as above:

Results are proportionate to the Standard A3 VM test, but they still fall far short.

I’m seeing 2.7 K IOPS instead of the expected 8K IOPS, and about 175 MB/s throughput instead of the expected 960 MB/s

The IOmeter ‘Maximum I/O response Time’ is extremely high (26+ seconds). This has been a consistent finding in all Azure VM testing. This leads me to suspect that the disk requests are being throttled (possibly by the hypervisor).

January 14, 2015 | Categories: Azure, Azure Storage, Benchmarking, Powershell, Storage, Storage Spaces | Tags: Azure, Azure standard A3 virtual machine, benchmark Azure VM storage, Powershell | 2 Comments