Virtual PC / SQL Server – Restore Database Failure – Media Family Incorrectly Formed

I ran into a problem with SQL Server restore operations recently.  I got burned for quite a while, because I thought I had a problem with my SQL Server 2000 and SQL Server 2005 installation, a SQL Server or O/S version issue, or a problem with my database backup file.  Small SQL backup files restore fine, but large backups fail on the restore on VPC images

When I restored the large backup files, ISQL RESTORE DATABASE commands fail with the following symptoms:

  • Msg 3241, Level 16, State 37, Line 1 The media family on device ‘C:\Temp\MyLargeDatabase.bak’ is incorrectly formed. SQL Server cannot process this media family.
  • The media set shows a Backup Set Name of *** INCOMPLETE ***
  • RESTORE HEADERONLY FROM DISK=’C:\Temp\MyLargeDatabase.bak’ returns BackupName of *** INCOMPLETE ***, Position = 1, the rest of the fields are NULL

The Problem

Virtual PC Shared Folders corrupt files!  Especially large files.  Small files seem to work fine.  I’ve heard reports of problems with files over 1GB to 4GB in size.  My database was around 8GB.

You get the errors shown above when you reference a file across a VPC Shared Folder, or when you create a local VPC file copy by copying a file to your VPC disk over a Shared Folder connection.

The Solution

Copy or reference files using a traditional networking file share between the host and guest, and avoid using Shared Folders for large files (or altogether).

Troubleshooting

If you think you may be having a similar issue, you can use a tool like SlavaSoft’s fsum to perform checksum comparisons file on the host and guest systems to verify what’s going on.  Or you can take my word for it and save yourself the trouble.  I’ve experienced this (the hard way) with Virtual PC 2007.

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4 responses to “Virtual PC / SQL Server – Restore Database Failure – Media Family Incorrectly Formed

  1. Brilliant. Couldn’t restore my sql db for the past week. This was exactly the solution

  2. Yup… thanks for posting. Helped me as well.

  3. Thank you, thank you

    I have been trying to work with 55 GB SQL 2k database for over 3 days trying to restore it to a virtual PC.

    There is lots of crap out there abouth this problem but no one posted something helpful like yours.

    Thank you again

  4. Thanks for the info. It truly met my needs. I copied the .rar file to my VPC from a shared drive and successfully restored the backup. Very frustrating (initially) after a few attempts of restores (probably more so for the customer). I even went out to the customer site to get the backup and that failed but this worked…thanks

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