Sign in with
Sign up | Sign in
Your question

size: versus size on disk:

  • Backup
  • HD
  • Windows XP
Last response: in Windows XP
February 18, 2006 1:45:59 AM

I copied a large directory to a backup drive, preparing to replace the HD on which the directory currently exists.

After copying, the "size" of source and target both match:
7.14 GB (7,673,318,222 bytes). The number of files and folders match as well.

However, the "size on disk" does NOT match.

On the source drive:
7.24 GB (7,783,518,208 bytes)

On the external (target) drive:
8.21 GB (8,821,047,296 bytes)

Is this a problem? Should I be concerned that the copy was not completed correctly?

More about : size versus size disk

February 18, 2006 1:50:32 AM

Access the files from the target drive and make sure they work alright, if they do I wouldn't worry about it.
February 18, 2006 1:58:08 AM

Thanks Russel. I wish I could realistically do that but there are 4806 folders and 43674 files.

Sounds like I may need to track down a file compare utility and run it overnight to determine any differences.

Any recommendations?
February 18, 2006 3:42:53 AM

ok, I found a program called FolderClone. After messing with settings so that it copies everything instead of ignoring hidden/system files/folders, I got a clean run:

2/17/2006 9:32:15 PM<Begin: compare D to H>
2/17/2006 9:35:17 PM<End: compare D to H> {All Activity Logged}

Regardless, I still have a difference:

D (source)
7.25 GB (7,790,862,336 bytes)

H (target)
8.22 GB (8,828,420,096 bytes)

How can this be? Is it explainable?
February 18, 2006 5:23:21 AM

Looks like there is a difference between the two drives. Perhaps the way they are formatted?

Anyway if you determine the files are copied correctly that's the big thing.
February 18, 2006 5:48:47 AM

D (internal) is NTFS.
H (external) is FAT32.

Is that the explanation? Is NTFS hgher density?
February 18, 2006 11:10:44 AM

There ya go! you found it.

Those are totally different preparations when formatting.
February 21, 2006 6:25:54 PM

More than likely its the cluster size thats different between the two drives.
If one drive is a 4k cluster and the other drive is say an 8k cluster then the same number of files will use up more space on the 8k drive.
Reason for this is a 1k file will use 1 full cluster, 4k.
So it would be 1k used in files but 4k total on disk. Hence the 8k cluster drive would use a full 8k to store that 1k file so you would be using 8k.

only one file can use a cluster at a time. Thats why if your using a lot of very small files a small cluster size is best to lessen lost disk space.
Bif files :ie 1mb or more, a larger cluster size is better.

Note: mentioned cluster sizez may not be possible on actual drives. just for reference
February 21, 2006 6:32:34 PM

thanks very much