Delayed Write Failed error with Windows XP VM using Shared Folders

[Mark Scarton]

I'm running a Windows XP VM in VirtualBox 2.1.4 under RedHat (RHEL) 5.3. It's on a very beefy box -- Dell M6400 quad core extreme with 12GB RAM and an SSD.

In general the VM runs great. More stable and faster than when Windows is running natively on my other laptop. The problem that I encounter is when I have active files located on a VB shared folder; I often will get a Delayed Write Failed error message and the files may be mangled. One file where this was occurring frequently was my primary Outlook data folder. I had to move it out of the shared folder and into the Windows dedicated C: drive.

I constructed the shared folder as follows:

1. Create a new partition on my secondary hard drive using RHEL fdisk command
2. Format the partition as an ext3
3. Mount the file system on Linux (as /windows_home)

In VirtualBox, I then defined the Shared Folder for the VM using the administration GUI tool. The folder shows up on Windows as a Network Attached Drive mapped to a drive letter. Typical nonintensive tasks can manipulate the files fine. But if an application updates the file frequently, such as an Outlook PST, xcopy of a large number of files to an alternate drive, Word save files, etc., I receive the delayed write error. Attempts to backup the folder from Windows using tools like xcopy and robocopy fail with this error too, and I get very nervous going more than a day or two without a complete, versioned backup of my work.

My intent is to be able to share access and update of these files concurrently from within Linux and Windows. I really don't want to be copying or synchronizing files between the environments, particularly since it is my intent to eventually be running 4-6 VM's concurrently. The complexity goes up exponentially with the number of VM's sharing the folder(s).

Please tell me what additional information I can supply to assist you with diagnosing and correcting this problem. If Shared Folders really aren't intended to be used with highly volative files, is there an alternative approach that you would recommend. Since this is exposed on Windows as a network drive, I don't know of any way to manipulate things like the Windows file caching strategy, etc. I did set the VBOX_DISABLE_HOST_DISK_CACHE=1 in my /etc/profile so that VirtualBox would inherit the setting, but that didn't seem to correct the issue.

I absolutely love the product. IMHO it's simple to use yet run's Windows in a VM far better than Windows is capable of running itself natively. I recommend it to all of my clients. So I'd really like to help you diagnose and fix this issue.

Thanks!