Robert McLaws: Windows Edition

Blogging about Windows since before Vista became a bad word

More on the WHS Corruption Bug (I've Been a Bad Beta Tester)

So the news making its way around the web in the slow news time between the holidays is that Microsoft posted a KB article about data corruption issues in WHS. I've been experiencing this problem consistently for a while now, but chalked it up to the way Outlook was accessing data on the file share, I didn't realize that it was a WHS issue. I probably should have bugged it in Connect much sooner.

But the problem is not as obscure as Ed Bott pointed out. It's actually relatively easy to reproduce. You see, I've kept pretty much every e-mail I've ever sent or received over the last 7 years. That amounts to just shy of 3GB of PST files. A while back I used the AutoArchive function on the AutoArchive files, to sort them into individual years, so that when I needed to get at old e-mails, the file wouldn't take FOREVER to open.

I thought my Home Server would be the perfect place to store these files. But it turns out, if you keep a PST AutoArchive file on WHS, and Outlook runs an AutoArchive, the PST file stays open in Outlook after it's done. If you've decided to keep your PST files safe by enabling Folder Duplication in WHS, and the DEMigrator service triggers a "balancing" while the file is open, your file is pretty much guaranteed to be corrupted. Usually ScanPST.exe will repair the file, but to be honest, there is no telling how much data that I have lost over the last 6 months of using WHS.

I've been experiencing this bug for a while, and I should have reported it sooner. I thought it was simply a factor of trying to use WHS during a balancing. For now, I have moved my PST files off of WHS, and you should too.

Also, don't save your Money 2007 files there either. I had two years worth of my business financials corrupted, along with their backups. I didn't realize WHS was the culprit until I read the KB article.



  • Ed Bott said:

    Robert, Microsoft has warned for years against opening any PST file from a network source. This article was originally published nearly eight years ago, if I recall correctly:

    It has been updated continuously since then and is unambiguous:

    "A .pst file is a file-access-driven method of message storage. File-access-driven means that the computer uses special file access commands that the operating system provides to read and write data to the file. ... If there is a remote .pst (over a network link), Microsoft Outlook tries to use the file commands to read from the file or write to the file, but the operating system then has to send those commands over the network because the file is not on the local computer. This creates a great deal of overhead and increases the time it takes to read and write to the file. Additionally, the use a .pst file over a network connection may result in a corrupted .pst file if the connection degrades or fails."

    The same KB article points to this blog post from the Windows Server Performance Team:

    Network Stored PST files ... don't do it!

    As for Microsoft Money, same advice from this MVP:

    "You can run Microsoft Money over the network (although it is not recommended due to network latency and the potential for corruption). It is not a supported configuration."

    December 30, 2007 1:32 PM
  • Ryan said:

    Robert: Another thing to point out, is that according to this KB (, you shouldn't be putting your PST file on any network share anyway.

    December 30, 2007 5:32 PM
  • Bob Cronin said:

    For what its worth, I had this same problem with my Thunderbird mail that I had moved to my WHS, and I did report it to Connect 3 to 4 weeks ago now, along with a hypothesis about it being caused by the balancing happening while the files were open. Good to see it has apparently been recreated by the WHS team.

    December 30, 2007 7:51 PM