Azure Storage and SQL Server – Part 6   Leave a comment


In the last post of this series, I had described how to determine if any database files were hosted on the temporary drive on the Azure virtual machine. In this post, I shall check if any of the drives hosting the SQL Server database files have block sizes other than 64KB. As per best practice recommendations for SQL Server workloads running on Azure virtual machines, it is recommended that you use a 64-KB allocation unit size for data and log files as well as tempdb.

Determining the block size

In the first part, I will be talking about how to determine if the block size for the drives hosting the database files is 64KB or not. The first thing that needs to be done is to retrieve the volume details using the Win32_Volume class and use the BlockSize value to determine the block size of the volume. To avoid false positives, you will also need the disks on which the SQL Server database files are hosted on. This can be retrieved using the sys.master_files system catalog. Using both the sets of information, you can determine if any volume that is hosting a SQL Server database file has a block size other than 64KB.

The PowerShell script that I had used is available below. This script also makes use of PowerShell snippet that I had used to identify the temporary drive which I had blogged about last week.


# Script for discovering temporary drive is available in Part 4 of this series

# Hence, not re-writing the script here

$TempDrive = "D:\"

# Fetching the disks on which the SQL database files reside on

$sqldisks = Invoke-Sqlcmd -ServerInstance "." -Database "master" -Query "select distinct substring(physical_name,0,4) as disk from sys.master_files" | Select-Object disk

# Getting the block size for each volume

$volumes = gwmi -Class Win32_Volume -Filter "DriveType = 3" | select-object BlockSize, Name

# Foreach loop to determine if block size for SQL disk drives vary from 64K

foreach ($volumne in $volumes)

{

if ($volumne.BlockSize -ne "65536" -and $volumne.Name.ToString() -In $sqldisks.disk)

{

if ($volumne.Name.ToString() -ne $TempDrive)

{

Write-Host "WARNING:" $volumne.Name "has a block size =" $volumne.BlockSize "bytes" -ForegroundColor Red

}

else

{

Write-Host "INFO:" $volumne.Name "has a block size =" $volumne.BlockSize "bytes. This is the temporary drive and should only host the tempdb files" -ForegroundColor Green

}

}

}

You might want to also read the following articles about disk partition alignment for SQL Server:
Disk Partition Alignment Best Practices for SQL Server
http://technet.microsoft.com/en-us/library/dd758814(v=SQL.100).aspx

Disk Partition Alignment: It Still Matters–DPA for Windows Server 2012, SQL Server 2012, and SQL Server 2014
http://blogs.msdn.com/b/jimmymay/archive/2014/03/14/disk-partition-alignment-for-windows-server-2012-sql-server-2012-and-sql-server-2014.aspx

Data and log files on the same drive

This is quite a common recommendation and has been taught to DBAs when they were in DBA elementary school! But sometimes, these recommendations are not followed for various reasons… some known and some unknown. So I decided that while I was at it, I would write up a quick PowerShell script to determine if the data and log files are present in the same drive using information retrieved from the sys.master_files catalog view.

The PowerShell script is give below along with a screenshot of the output.


$sqldisks = Invoke-Sqlcmd -ServerInstance "." -Database "master" -Query "select distinct substring(physical_name,0,4) as disk, type_desc from sys.master_files"

$datafiles = $sqldisks | Where-Object {$_.type_desc -eq "ROWS" }

$logfiles = $sqldisks | Where-Object {$_.type_desc -eq "LOG" }

if ($datafiles.disk -contains $logfiles.disk)

{

Write-Host "ISSUE: Data and log files found on the same drive" -ForegroundColor Red

foreach($drive in $datafiles)

{

if ($drive.disk -contains $logfiles.disk)

{

Write-Host "ISSUE: Drive" $drive.disk "hosts data and log files" -ForegroundColor Red

}

}

}

image

Previous post in the series

Azure Storage and SQL Server – Part 1
http://troubleshootingsql.com/2014/11/10/azure-storage-for-sql-server/
Azure Storage and SQL Server – Part 2
http://troubleshootingsql.com/2014/11/11/azure-storage-and-sql-server-part-2
Azure Storage and SQL Server – Part 3
http://troubleshootingsql.com/2014/11/12/azure-storage-and-sql-server-part-3
Azure Storage and SQL Server – Part 4
http://troubleshootingsql.com/2014/11/13/azure-storage-and-sql-server-part-4/
Azure Storage and SQL Server – Part 5
http://troubleshootingsql.com/2014/11/18/azure-storage-and-sql-server-part-5

References

Azure Storage
http://azure.microsoft.com/en-us/services/storage/
Azure Subscription and Service Limits, Quotas, and Constraints
http://azure.microsoft.com/en-us/documentation/articles/azure-subscription-service-limits/#storagelimits

* This blog post has been written based on the service details available on 16th November, 2014.

Posted November 19, 2014 by Amit Banerjee in Azure, IaaS, Powershell

Tagged with , , ,

Azure Storage and SQL Server – Part 5   1 comment


In this post, we will start checking if the SQL Server files are following best practices for Azure storage recommendations. In Part 4 of this series, I had written about how to identify the temporary drive on an Azure Virtual Machine. I am going to use that snippet of code to perform the file layout test that I will perform here.

The script performs the following operations:

1. Finds out the temporary drive letter

2. The script first finds out if the Azure Virtual Machine is a D-series machine or not.

3. Then it fetches the file location from the SQL Server instance using the Invoke-Sqlcmd cmdlet.

4. Using the above information, it determines if files are present on the temporary drive or not.

If this is a D-Series virtual machine, then the script will not report a warning if it finds the tempdb files on the temporary drive as it is supported. For any other series, the script will report an issue since database files residing on the temporary drive are not supported on the temporary drive other than the D-Series.

The PowerShell script is available below:


# Find out the IDE drives on the machine which has a SCSI target = 1

$Name = Get-WmiObject -Class Win32_DiskDrive -Filter "InterfaceType = `"IDE`" and SCSITargetId = 1" | Select-Object Name

# Find the parition id corresponding to the IDE temporary drive

$Antecedent = "*" + $Name.Name.Replace("\","").Replace(".","") + "*"

$Dependent = Get-WmiObject -Class Win32_DiskDriveToDiskPartition | Where-Object {$_.Antecedent -like $Antecedent} | Select-Object Dependent

# Find the logical disk which corresponds to the temporary drive partition

$Antecedent = "*" + $Dependent.Dependent.Split("`"")[1] + "*"

$TempDrive = (Get-WmiObject -Class Win32_LogicalDiskToPartition | Where-Object {$_.Antecedent -like $Antecedent} | Select-Object Dependent).Dependent.Split("`"")[1]

Write-Host "INFO: Temporary drive on the machine is:" $TempDrive -Foregroundcolor Red

# Variable to track if this is a D-Series VM

[boolean] $DSeries = $false

# Using Get-AzureVM to get the instance size property

$InstanceSize = Get-AzureVM -ServiceName "<azure service name>" -Name "<azure vm name>" | Select-Object InstanceSize

# Find out if this is a D-Series VM

if ($InstanceSize.InstanceSize -like "*_D*")

{

$DSeries = $true

}

# Get the location of the database files from the system catalog

$dbfiles = Invoke-Sqlcmd -ServerInstance "." -Database "master" -Query "select physical_name, name, db_name(database_id) as dbname, type_desc from sys.master_files"

# Run a foreach loop to determine if any user or system database files are on the temporary drive other than the tempdb

foreach ($file in $dbfiles)

{

# Tempdb can be hosted on the temporary drive on D-Series VMs

if ($DSeries-eq $true)

{

if ($file.physical_name.substring(0,2) -eq $TempDrive -and $file.dbname -ne "tempdb")

{

Write-Host "ISSUE:" $file.dbname "(Filename:" $file.name " Location:" $file.physical_name") found on temporary drive" $TempDrive -ForegroundColor Red

}

}

# Report any databases on temporary drive for non-D-Series VMs

else

{

if ($file.physical_name.substring(0,2) -eq $TempDrive)

{

Write-Host "ISSUE:" $file.dbname "(Filename:" $file.name " Location:" $file.physical_name") found on temporary drive" $TempDrive -ForegroundColor Red

}

}

}

Please keep in mind that the above script has not been tested for mount points.

Previous post in the series

Azure Storage and SQL Server – Part 1
http://troubleshootingsql.com/2014/11/10/azure-storage-for-sql-server/
Azure Storage and SQL Server – Part 2
http://troubleshootingsql.com/2014/11/11/azure-storage-and-sql-server-part-2
Azure Storage and SQL Server – Part 3
http://troubleshootingsql.com/2014/11/12/azure-storage-and-sql-server-part-3
Azure Storage and SQL Server – Part 4
http://troubleshootingsql.com/2014/11/13/azure-storage-and-sql-server-part-4/

References

Azure Storage
http://azure.microsoft.com/en-us/services/storage/

Azure Subscription and Service Limits, Quotas, and Constraints
http://azure.microsoft.com/en-us/documentation/articles/azure-subscription-service-limits/#storagelimits

* This blog post has been written based on the service details available on 10th November, 2014.

Posted November 18, 2014 by Amit Banerjee in Azure, IaaS, Powershell

Tagged with , , , ,

GOTCHA: Executing powershell scripts using scheduled tasks   Leave a comment


This is another gotcha for setting up scheduled tasks which execute PowerShell scripts. I have a SQL Server instance installed on an Azure virtual machine. I am using a D-Series machine which allows me to store my tempdb files on the D: drive which is a SSD drive. However, the D: drive on Azure virtual machines is not a persistent drive. If you have change the drive letters on your Azure VM, then you can use the PowerShell script in my earlier blog post to identify the temporary drive. So, when the Azure virtual machine restarts the D: drive is re-created and all my folder structure is lost. I already have a scheduled task created on my Azure virtual machine which re-creates the folder structure on the D: drive. The blog post in the reference section has more details on how to achieve this.

However, when the scheduled task executes, the following error is reported in the Task Scheduler logs.

image

The last run result is reported as 0xFFFD0000 and the task history would show the following message:

Task Scheduler successfully completed task “\Tempdb Folder Creation” , instance “{35ec7a4f-6669-437f-b12f-40b95689896c}” , action “C:\Windows\System32\WindowsPowerShell\v1.0\powershell.EXE” with return code 4294770688.

First, let us find out why this error message gets reported. If you have setup a PowerShell script to execute the script in the following manner using single quotes, then this issue occurs.

powershell -file ‘C:\Automation\TempdbFolder.ps1′

If you have not used an output file, then you will find that this might not be an easy thing to troubleshoot. If you execute the above command from a command prompt window, you will find the following error reported:

Processing -File ”C:\Automation\TempdbFolder.ps1” failed: The given path’s format is not supported. Specify a valid path for the -File parameter.

Changing the command to use double quotes would make it execute without any issues.

Some other things to keep in mind when creating the scheduled task would be:

1. Using a full qualified path to the script file rather than a relative path.

2. Ensuring that the account running the script has the correct privileges.

3. The task should be configured to run without having the user logged in.

Reference:
Using SSDs in Azure VMs to store SQL Server TempDB and Buffer Pool Extensions
http://blogs.technet.com/b/dataplatforminsider/archive/2014/09/25/using-ssds-in-azure-vms-to-store-sql-server-tempdb-and-buffer-pool-extensions.aspx

Posted November 17, 2014 by Amit Banerjee in IaaS, Troubleshooting SQL Issues

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