Nearly three months have passed since Microsoft announced that Windows Home Server (WHS) had a file-corruption problem. Microsoft has dutifully kept us in the loop as it learns more about the problem and has mentioned that we might see a fix in June (at the earliest)--a full 6 months after the company acknowledged the bug. You might be asking, “What the heck is taking so long!?”

When I first heard about the problem, I wasn’t concerned. Our friends in Redmond deal with these kinds of problems all the time; how long could it take? How complicated could the fix be?

But June?

To find out the reason for the long wait, I searched online for some details and later even contacted Microsoft’s WHS PR firm to get some answers. I knew that WHS was built upon Microsoft Small Business Server (SBS) 2003, and SBS was built on top of Windows Server 2003. Neither of these platforms suffers from the file-corruption problem, so why is WHS vulnerable?

My first clue occurred when I logged on to the server via Remote Desktop. Instead of seeing a blank desktop, I was immediately faced with a stern warning: Many standard Windows Server administration tools available from this desktop can break Windows Home Server. Read the Release Documentation before you use any tool on this desktop and proceed with caution.

At first, I didn’t believe the warning. Because this product is aimed at everyday home users, I assumed this was Microsoft’s way of reducing the number of support calls it received. So, instead of logging onto the server, I reverted to using the console for safely performing administrative tasks.

Why can’t we use standard administrative tools such as Disk Manager in WHS? Again, the answer lies in WHS’s target customer: the average home user. When it comes to disks and disk management, Microsoft wanted to introduce a different paradigm than classic RAID. WHS needed to let users add additional hard disks and remove older, smaller disks, all while presenting to that user one set of network shares that appeared to grow and grow. WHS also needed a way for users to protect important files in case of a hard disk failure.

To accomplish this feat, Microsoft came up with a new technology called Windows Home Server Drive Extender. This technology takes care of the important “behind the scenes” work that happens when a user adds or removes an internal or external disk drive. WHS servers with single hard disks have it easy: The disk’s first 20GB is partitioned out for the OS, and the rest is used for data storage. This data-storage area is called the primary data partition, and WHS simply stores files there.

As soon as the user adds a second hard disk, the story gets a little more interesting. The files that were located on the primary data partition become small 4KB “pointers” (Microsoft calls them “tombstones”), and the system copies the actual files to the additional drive. For added protection from a hard disk failure, you can enable Protected Storage to ensure that your important files reside on two physical disks. The file will appear to live in the share on the primary data partition, but in reality the system stores the file on a separate disk or disks. This sleight of hand gives the appearance that the primary data partition just keeps growing larger and larger.

For this reason, it’s very important that you don’t use tools such as Disk Manager to try to manipulate the hard disks. It’s also important to use caution when using Windows Explorer when you’re logged on to the server. To be safe, be sure to access the files via the network share (e.g., \\server1\public, \\server1\software). This way, you’ll connect to the tombstone files, and WHS Drive Extender will take care of everything in the background for you.

If all this sounds complicated, that’s because it is. Microsoft has a 20-page technical brief that thoroughly breaks down the technology. But even at this basic level, you can see that there must be a lot going on in the inner-workings of the server to ensure that it sets the tombstone correctly and copies the actual data to the correct drive. This “redirection mechanism,” as Microsoft calls it, has the bug that’s causing the data corruption. The Microsoft article “When certain programs are used to edit or transfer files that are stored on a Windows Home Server-based computer that has more than one hard drive, the files may become corrupted” states the following: “A bug has been discovered in the redirection mechanism which, in certain cases, depending on application use patterns, timing, and workload, may cause interactions between NTFS, the Memory Manager, and the Cache Manager to get out of sync.” In other words, if the conditions are just right, when the system is updating the tombstone and the actual file, something goes haywire. Instead of good, clean data being applied to the file, it gets corrupted instead.

Now that you know a little bit about how this “redirection mechanism” works, you’ll have a better understanding why the fix is taking so long. But you don’t have to be happy about it.

Article Information

Email this Article Printer-Friendly

Reader Comments
Hey, is this why i periodically get a message that there are hard disk errors? I bought the HP unit with 500G base drive and added two 1TB drives. Periodically it tells me to run a some sort of utility (can't remember) and then it says the drive is "all better now." Should i believe it? Is my data safe? Sanders Partee -March 19, 2008 I have been building my own WHS in hopes of replacing an outdated server, but this model does make some things more difficult. The first problem that WHS does not solve the “what happens if the boot HD fails?” If you take a look at the drive manager you would notice that if that happens you would be in big trouble. WHS does not automatically provide RAID 1, mirroring, of the system drive. This paradigm also makes running other server oriented tools a little tough. Say I want a CVS server to run there. How about a DDNS client? It is not overly clear what can and cannot be done. I will continue to play… Chirs -March 19, 2008 One more thing … I suspect that this mapping is also the reason that path names longer than 250 characters causes a problem with the “Drive health” status. Chris -March 19, 2008 Chris, Those are all good questions. I'll see what I can come up with. Oh, and it's 240 characters (according to the WHS Tech Brief that I read) Eric B. Rux -March 19, 2008 Sanders, I have the same unit, and I'm getting ready to add some drives too. I'll report back what I find out.... Thanks for the feedback! Eric B. Rux -March 19, 2008 I took an old machine, threw a couple of hard drives in it, and installed the trial version of Windows Home Server. So far, it's running like a dream. The trial allows for 120 days of use, so it'll get a good workout. Jim -March 19, 2008 I had originally read that the bug only surfaced on WHS systems where folder duplication was enabled. Your article makes it clear that the problem is with any WHS system that has multiple drives and I can confirm this. I had added a second 500 gb drive to my HP MediaSmart server last week. My Outlook PST file and my Quicken 2007 data files both developed consistency errors the very next time I used them. I was able to run the ScanPST and Quicken verify functions to correct the errors but then had to move those two data sets off the WHS and onto my local machine. Looking forward to the patch. Other than that I really like WHS. Randy -March 24, 2008 I have been running a WHS since beta (running on an old Dell FF), I have currently attached (2) 500GB and (1) 350GB drives (just what I had lying around at the time) via USB and have not been subjected to any corruption issues. And yes, I know they exist… While I have not used any of the programs mentioned in the KB article to save data to WHS, I have moved a good deal of Data to them as well (iTunes backups – Scanned Documents – Pics – along with many progs, DBs, and other data) with no corruption issues. Also the server is backing up 2 laptops and 1 desktop. One improvement I would suggest for WHS is to have an easily accessible way to backup to external media. This would allow a great deal of relief to WHS users until the fix is released and allow users to get backups off disk and offsite. Another option would be to allow for a functionality to interact with SkyDrive and push backups into the cloud. Running a little long here, so I will step down now. :) Dan -April 8, 2008 Great feedback, Dan. THANKS. The "Power Pack" is supposed to have the "backup the backup" feature that you are requesting. I'm trying to get my hands on a pre-release copy..... Standby to standby... :-) Eric B. Rux -April 9, 2008 I'm using WHS with 3 SATA-drives. The first drive with the system is a raptor 74gb. The two other ones are 500gb each. The strange thing is that I can't transfer more data to the server than the raptor can hold. It makes no difference if I use the consol, shared folders or anything else. The two others drives are reported to be healthy, and the total storage space is round 1tb. But can't copy more than 50gb of data before it says there no space for it. Anyone? Simeon -July 21, 2008 The reason for this is that the WHS OS uses the first drive as a landing pad for all file transfers. Your first drive is approx. 74 GB broken into 20 GB for the OS and about 50 GB remaining. That would limit your max file transfer to around 50 GB. Teckset -February 27, 2009 Your Comments (required): Name (required): -July 5, 2009 This problem is NOT FIXED. I have 20 years in IT and i am removing WHS. I have lost files for the 5th time due to tombsotone / access denied crap.. i'm SICK of IT. Hardware ran fine for months with SBS and win2k3. This program has issues with length of file path, and still data corruption. I posted it on the WHS support and they closed the ticket. WTF??? I can and have duplicated this problem. FIX IT! (it does it with no paower pack and with powerpacks) PS I am running OEM version with powerpack 3. Mitch -January 26, 2010 READER COMMENTS: We want to hear what you have to say about this article!     Acceptable Use Policy Your Comments (required): Your email is only used if our editors need to contact you. It is not used or stored for any other purpose, nor posted with your comments. Enter the text from the image below Please refresh the page if you have trouble reading this text.