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Why can I only back up a maximum of 4 gigabytes?

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?

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.”

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.

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7 comments on “Why can I only back up a maximum of 4 gigabytes?”

  1. So what will come after NTFS?
    Files sizes are becoming so huge now (a Blue-ray movie is typically 45gb) and the size of Hard Drives getting bigger.
    What happens when people want to back that much data up?

    Reply
  2. Eeveevolve–

    I have a feeling that the 2TB limit won’t be a problem for a couple years yet.
    Supposedly Windows is releasing WFS (Windows File System). They stripped it from Vista, but it is supposed to get around that limitation (on the off chance it’s a problem).

    JFS, however, has a limit for the file size of 4 Petabytes (4000 TB). (according to wikipedia: http://en.wikipedia.org/wiki/JFS_(file_system))

    –Zigg

    Reply
  3. 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.)

    Reply
  4. That 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.

    Reply
  5. 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.

    Not at all, you simply need to type in the current label for the external drive. This article talks about what that is, and how to create one if the drive is unlabelled: What’s a Volume Name?

    Leo
    05-Dec-2009

    Reply
  6. 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
    system was converted and I could backup the file.
    GREAT explanation.

    Reply

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