Jason Slater Weblog

For some time I have been backing up our Exchange Information Store using Microsoft Backup and storing it on external USB hard drives (Retrieving data quickly) for safe keeping off site (as well as keeping an electronic copy of it on another server). Recently though the following message has started to appear when copying the backup file (.bkf) to the USB hard drive device.

Insufficient disk space exits to continue the current operation. Please free some disk space and retry the operation.

This is an odd message as there was clearly plenty of space on the drives. It took a few moments for the penny to drop. It seems our backup file has tripped over the 4GB FAT32 file size limit and as the external USB drives are formatted to FAT32 the message was being reported (Formatting the drives to NTFS would add a little more complexity to the proceedings).

The following Microsoft Tech note sheds more light on this situation: http://support.microsoft.com/kb/250651

There are a number of possibilities to deal with this problem:

• Create multiple information stores and back them up separately
• Split the backup (.bkf) file into 4GB blocks
• Use a different backup package that is more configurable
• Rethink the entire backup strategy

My first approach is to simply split the file into smaller 4GB or less blocks. I have tried several products and they are all quite slow but the most promising one so far  is GSplit (http://www.gdgsoft.com/gsplit/) from G.D.G. Software (I especially like the handy Explorer context menu), a free application that describes itself as:

"…lets you split your large files (like Self-Extracting archives, Zip archives, multimedia, song, music, movie, backup, picture, archive, log, large text, document files…) into a set of smaller files…"

Upon completion I am presented with a number of files all tied together with a handy executable file for joining them back together.