Use PowerCLI to find the datastore from a disk name

Recently we get vSphere alarms in our environment that say for instance:

“[VMware vCenter – Alarm Host error] Issue detected on host in datastore: ScsiDeviceIO: 2368: Failed write command to write-quiesced partition naa.600a0b8000111155000021c53f97784e:1 (42:01:04:07.994 cpu7:5191)”

There seems to be a problem on a partition. But which datastore is on this partition? We can use PowerCLI to find the datastore involved.

List all datastores and disk names

We can use the PowerCLI script from listing 1 to list all datastores and the disk names of the partitions.

Get-Datastore |
Where-Object {$_.ExtensionData.Info.GetType().Name -eq "VmfsDatastoreInfo"} |
ForEach-Object {
  if ($_)
  {
    $Datastore = $_
    $Datastore.ExtensionData.Info.Vmfs.Extent |
    Select-Object -Property @{Name="Name";Expression={$Datastore.Name}},
      DiskName
  }
}

Listing 1. PowerCLI script to list all datastores and the disk names of the partitions.

A sample output of this script is:

Name                        DiskName
----                        --------
esxi01_boot                 naa.600a0b80001111550000fb9cf54f414d
esxi02_boot                 naa.600a0b80001111550000850e884f414d
cluster01_gold_001          naa.600a0b80001111550000778bc952494d
cluster01_silver_001        naa.600a0b8000111155000074088c52494d
cluster01_bronze_003        naa.600a0b80001111550000e451a8ed794e
esxi03_boot                 naa.600508b4001078340000e00004c00000
esxi04_boot                 naa.600508b4001078340000e00002c60000
cluster02_gold_001          naa.600508b400055c680000800000dc0000
cluster02_silver_001        naa.600508b4001078340000e00004bb0000
cluster02_bronze_001        naa.600508b4001078340000e00002cb0000

Output 1. Sample output from the PowerCLI script from listing 1.

Of course you can try to find the diskname and the corresponding datastore in the list. But if the list is long this is not easy.

A better way is to let PowerCLI do the search.

Find a specific datastore

The PowerCLI from listing 2 shows returns only the datastore that contains the partition with the requested disk name.

Get-Datastore |
Where-Object {$_.ExtensionData.Info.GetType().Name -eq "VmfsDatastoreInfo"} |
ForEach-Object {
  if ($_)
  {
    $Datastore = $_
    $Datastore.ExtensionData.Info.Vmfs.Extent |
      Where-Object {$_.DiskName -eq "naa.600a0b80001111550000fb9cf54f414d"} |
      ForEach-Object {
        if ($_)
        {
          $Datastore
        }
      }
  }
}

Listing 2. PowerCLI script to get the datastore that contains the partion with the requested disk name.

Unfortunately the script from listing 2 is slow. In our environment with 138 datastores the script takes 43 seconds to run.

A faster script

I decided to make a PowerCLI advanced function that searches for the datastore as fast as possible. It uses the PowerCLI Get-View cmdlet to retrieve all the datastores. It then tries to match the datastores in this list with the given disk name.

function Get-DatastoreByDiskName {
  <#
  .SYNOPSIS
    Retrieves the datastore for a given disk name.
	
  .DESCRIPTION
    Retrieves the datastore for a given disk name.
	
  .PARAMETER DiskName
    Specify the disk name of the partition in the datastore to search for.
	
  .EXAMPLE
    Get-DatastoreByDiskName -DiskName naa.600a0b80001111550000a3fdfb4e6c4f
    Retrieves the datastore with disk name naa.600a0b80001111550000a3fdfb4e6c4f.
	
  .EXAMPLE
    "naa.600a0b800011115500006852e34d6c4f" | Get-DatastoreByDiskName
    Retrieves the datastore with disk name naa.600a0b800011115500006852e34d6c4f.
	
  .COMPONENT
    VMware vSphere PowerCLI

  .INPUTS
    String
	
  .OUTPUTS
    VmfsDatastoreImpl

  .NOTES
    Author:  Robert van den Nieuwendijk
    Date:    1-6-2012
    Version: 1.0

  .LINK
    https://rvdnieuwendijk.com/
    http://twitter.com/rvdnieuwendijk
	
  #>
  
  [CmdletBinding()]
  param(
    [parameter(Mandatory = $true,
               ValueFromPipeline = $true,
               ValueFromPipelineByPropertyName = $true)]
    [string[]] $DiskName
  )
  
  begin {	
    # Get all the datastores
    $DatastoresView = Get-View -ViewType Datastore -Property Name,Info
  }
  
  process {
    ForEach ($Datastore in $DatastoresView)
    {
      # Only objects of type VMware.Vim.DatastoreInfo.VmfsDatastoreInfo
      # have the Info.Vmfs property
      if ($Datastore.Info.GetType().Name -eq "VmfsDatastoreInfo")
      {
        ForEach ($Disk in $DiskName)
        {
          $Datastore.Info.Vmfs.Extent |
            ForEach-Object {
              if ($_ -and $_.Diskname -eq $Disk)
              {
                # Return the found datastore
                $Datastore | Get-VIObjectByVIView 
              }
            }
        }
      }
    }
  }
}

Listing 3. A PowerCLI advanced function that searches for the datastore as fast as possible.

This script finds one datastore in 1.5 seconds. That is 29 times faster than the script from listing 2.

You can use the advanced function to search for multiple datastores at once. Every extra datastore took me 1.1 seconds extra.

Annotations

Line 50: Get all the datastores.

Line 54-72: Loop through all the datastores.

Line 60-70: Loop through all the disk names.

Line 67: Return the found datastore.

Conclusion

We have not solved the issue from our vCenter alarm yet. But it least we now know which datastores are involved.

Writing PowerCLI code for maximum speed can make your code significantly faster.

Update Januari 2nd, 2013: Thanks to reader Brad S. who commented on a problem that was in the original script of listing 1, I could solve the bug in this script. I updated the scripts in listing 1 and listing 2 to work correctly with datastores that have multiple extents.