Finding Differences in Exchange objects (#DoExTip)

Many times, when I’m troubleshooting Exchange issues I need to compare objects (such as user accounts in Active Directory, or mailboxes) to figure out why there is a difference in behavior. Many times, the difference is tiny and hard-to-spot. It may not even be visible through the GUI.

To do this, I first dump the objects to separate text files. How I do this depends on the type of object I need to compare. If I can output the object using Exchange Management Shell, I pipe it through Format-List and dump it to text there:

Get-Mailbox –Identity Devin | fl > Mailbox1.txt

If it’s a raw Active Directory object I need, I use the built-in Windows LDP tool and copy and paste the text dump to separate files in a text editor.

Once the objects are in text file format, I use a text comparison tool, such as the built-in comparison tool in my preferred text editor (UltraEdit) or the standalone tool WinDiff.The key here is to quickly highlight the differences. Many of those differences aren’t important (metadata such as last time updated, etc.) but I can spend my time quickly looking over the properties that are different, rather than brute-force comparing everything about the different objects.

I can hear many of you suggesting other ways of doing this:

  • Why are you using text outputs even in PowerShell? Why not export to XML or CSV?
    If I dump to text, PowerShell displays the values of multi-value properties and other property types that it doesn’t show if I export the object to XML or CSV. This is very annoying, as the missing values are typically the source of the key difference. Also, text files are easy for my customers to generate, bundle, and email to me without any worries that virus scanners or other security policies might intercept them.
  • Why do you run PowerShell cmdlets through Format-List?
    To make sure I have a single property per line of text file. This helps ensure that the text file runs through WinDiff properly.
  • Why do you run Active Directory dumps through LDP?
    Because LDP will dump practically any LDAP property and value as raw text as I access a given object in Active Directory. I can easily walk a customer through using LDP and pasting the results into Notepad while browsing to the objects graphically, as per ADSIedit. There are command line tools that will export in other formats such as LDIF, but those are typically overkill and harder to use while browsing for what you need (you typically have to specify object DNs).
  • PowerShell has a Compare-Object cmdlet. Why don’t you use that for comparisons instead of WinDiff or text editors?
    First, it only works for PowerShell objects, and I want a consistent technique I can use for anything I can dump to text in a regular format. Second, Compare-Object changes its output depending on the object format you’re comparing, potentially making the comparison useless. Third, while Compare-Object is wildly powerful because it can hook into the full PowerShell toolset (sorting, filters, etc.) this complexity can eat up a lot of time fine-tuning your command when the whole point is to save time. Fourth, WinDiff output is easy to show customers. For all of these reasons, WinDiff is good enough.