Tuesday, March 11, 2008

Windows Home Server Data Corruption Fix Coming, in June

We've written several times since late December about the file corruption issues that have plagued Windows Home Server - not a good thing for a file server, right? On Monday Microsoft indicated on the Windows Server Team Blog that they understand the problem "really well," and that they will have a fix - though not until June.

Of course, some people probably wonder why it's taking so long to fix, as this issue will have been known for six months before the fix will appear. Data corruption in an OS, obviously not an easy thing to find or fix, and I'm sure they want to get it right (this time) so extensive testing will be required. From the blog post:
From the outside looking in, some people would say “Why is this taking so long?” Fixing this issue is the Windows Home Server team’s top priority and the team is making good progress on the fix. We understand the issue really well at this point - it is at an extremely low level of the operating system and it requires thorough testing to ensure that the fix addresses the issue. We have coded a part of the fix which is currently being tested internally. Internal testing is expected to continue for at least several more weeks.

Once the patch has passed internal quality bars, external participants will be asked to help test the fix. Our current plan is to release beta test versions of a fix over the next few months, with a final version currently estimated for June 2008, although that date could change as testing progresses. Thorough testing of the fix is critical and will take time.
The KB946676 article gets a lot more detailed, pointing to Windows Home Server’s Drive Extender technology which many have suspected:
Windows Home Server uses a file system mini-filter driver in addition to the NTFS file system to implement Shared Folders storage technology. File system mini-filter drivers are an extensibility mechanism that is provided by Windows to enable storage scenarios. For distributing data across the different hard drives that are managed by Windows Home Server, the Windows Home Server mini-filter driver redirects I/O between files that are stored on the main hard drive and files that are stored on other hard drives. This redirection mechanism is enabled only when Windows Home Server is managing the Shared Folder storage of multiple physical hard drives. 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. This causes corrupted data to be written to files.
And here's some fun stuff to be used as a workaround / preventative.
As a precautionary measure, users should use Windows Explorer or a command-line tool to copy files to and from the Windows Home Server-based computer. Do not use applications to directly edit or change files that are stored on the Windows Home Server-based computer.

Users may consider setting Shared Folders on Windows Home Server to read-only and avoid using media management programs, such as Windows Media Player, to import files to the home server. They may also want to avoid redirecting applications to access files that are stored in the Shared Folders because some applications may change the metadata of a file without explicit user action.
So don't use files directly on the Home Server. Wonderful way to use a file server, wouldn't you say?

They also indicate they will be using external beta testers once the fix has passed an internal screening, so if you've complained already about this issue - you might be on their short list.

Once again, isn't a NAS so much easier than all this?

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