Helping people with computers... one answer at a time.
When backing up large amounts of data the filesystem used on the backup media matters. FAT32 often can't handle the way that many backup programs work.
I have downloaded a backup program for Windows XP Home Edition. A differential backup of the C drive & System Settings to an external 250gb hard drive fails with a message that the drive is formatted as Fat 32 & the maximum backup is 4gb. There is plenty of space on the external drive. How do I backup 40 gigabytes?
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Actually the clue is right there in the error message: the problem is FAT32.
Fortunately the solution is fairly straightforward.
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FAT32 is what's called a "file system" which specifies exactly how files are laid out on a hard disk. By that I mean that it defines where the computer would go to look for the names of files and folders stored on the disk and how the computer locates the data on the hard disk associated with the files and folders that it finds.
FAT32 (which stands for "File Allocation Table, 32 bit version") is actually fairly old and was devised as a easily upwards compatible version of its predecessors FAT16 and FAT12. FAT12 actually dates back some 30 years.
One of the limitations of FAT32 is simply this: a single file can be no greater than 1 byte short of 4 gigabytes.
My guess is that your backup program is attempting to write its backup in to a single file, and as a result that file is exceeding that 4 gigabyte limit. Fortunately it's nice enough to point out the exact problem: that FAT32 is at the root of the problem.
Since you're using Windows XP, the solution is actually quite simple: convert the hard disks format from FAT32 to NTFS.
NTFS (for New Technology File System) was introduced with Windows NT in the early 1990's. Among other things it replaces the 4 gigabyte file size limit with 2 terrabytes or 2,048 gigabytes. That should be sufficient for your needs, as it's roughly 8 times bigger than your 250 gigabyte hard drive.
Converting your external drive to NTFS is simple. Open a Windows Command Prompt and enter the following command:
CONVERT E: /FS:NTFS
Be sure to replace "E:" with the actual drive letter that corresponds to your external drive.
The convert utility converts everything in place with no data loss. If you'd rather, you can also reformat your external hard drive to NTFS, but that will of course erase the contents of the drive in the process.
Once the external drive is formatted as NTFS your backup program should have no problems writing out that 40 gigabyte backup file.
Coincidentally, that's exactly what I have on my external hard drive.
Article C3213 - November 15, 2007
Leo A. Notenboom has been playing with computers since he
was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed.
After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers
to common computer and technical questions. More about Leo.
Ziggie: actually, NTFS's theoretical maximum file size limit is 16 *exa*bytes, over 4000 times bigger than JFS's limit. It's only in the current implementation that you're limited to 16 (not 2) terabytes.
(Besides, it's not as if Microsoft might switch to JFS, as it's an inferior file system to NTFS in a number ways -- no file changelog, no internal snapshotting, doesn't support transparent compression, doesn't support filesystem encryption... etc.)
Posted by: Simon at November 19, 2007 5:58 PMThat answers why Acronis made around 36 files rather than one big one on my new external HD. That's one question answered! If Acronis mentions this in their software, I missed it.
Posted by: Steve Bukosky at December 29, 2008 5:04 PMwhere is the command prompt?
24-Jun-2009
Posted by: Valerie at June 23, 2009 8:27 AM
Leo,
I am running Windows XP & have bought an external hard drive to perform a full back up, the hard drive came with Nero BACKITUP software. The booklet states the external drive is formatted in FAT32 format. I have tried to use the Windows XP back up utilty, not Nero, and get the 4GB error message. I have tried to convert my external drive to NTFS as suggested by entering CONVERT F: /FS:NTFS but receive another message in DOS 'Enter Current volume label for drive F:' - am I missing something?
Thanks.
05-Dec-2009
Posted by: Ged McDonald at December 4, 2009 8:49 AM
EXCELLENT explanation on the file system issue.
I recently got a 16GB flash drive and I've been meaning to backup my VMWare Ubuntu image. I was going crazy since it wouldn't let me copy it over.
That line you mentioned:
CONVERT E: /FS:NTFS
worked like a charm! In about a minute the file
Posted by: Omar at March 18, 2010 10:52 PMsystem was converted and I could backup the file.
GREAT explanation.