HDD doesn't show the free space it should have

[ovi]

All the HDDs in my computer tell me, when I select all the data (including the hidden folders) a certain size. Let's say HDD 1 has 160GB with 50 Gb of data in it. Instead of showing 110 Gb free it tells me I only have about 20 Gb free. A huge discrepancy ! With all my disks and partitions. They've all been properly formated and before I add any files to a hdd it tells me the right amount of free space. Once I start adding files though ... if I add a 1Gb file it immediately acts as if my free space has been reduced with almost 2 Gb.

I've used a lot of programs to try and identify any hidden folders, or to recheck the proper readings but they're all consistent.

The drives show that they have D amount of data in them out of a total T. The free space though F is different than T-D. How can this be?

Can anybody help?

 

[ovi]

can anybody help me with this?

 

[rcs2749]

can anybody help me with this?

Run a complete disk check on the drives. Check disk will sometimes find errors in the free space and fix it.

 

[Sciberpunkt]

Maybe a size barrier issue with the BIOS?

http://www.dewassoc.com/kbase/hard_drives/hard_drive_size_barriers.htm

How old is the PC?

 

[hammerhead2]

the short answer is a 1 gig file may take 1 gig of space or it might take
more,
depends on several things ,, how did you format your drives
fat32,, ntfs,,other?? what block size depending on the format
and disk size you may have sector sizes of 4k to 64k ,,also size of the files you are saving,, a large number of small files may take for more than the total size of all the files

example you save a file of 65 kilobytes on a machine with a sector size
of 64 kilobytes the file will fill 1 sector and part of another,, but the rest of
the second sector is now unavailable , 65 kb takes 128 kb total space

also if you have partitioned a drive say 160 gig to 60gig and the balance in a second so the space left maybe correct for the partition but not reflect the whole drive cap
also drive cap reported will be in ms gig (1073741824) not drive manufacter gig (1,000,000,000) so totals will not match

there maybe a better explination on here somewhere

 

[ragemonkey]

You won't be able to calculate free space by simply applying your equation. Unfortunately with hard disks it's not that easy.

First, Hard Disks are advertised with storage capacities given in Decimal Gigabytes (base 10) and Windows calculates total/free space in Binary Gigabytes (base 2).

The difference is:

Advertised == 1(bit) x 8(byte) x 1000(kilo) x 1000(mega) x 1000(giga)
Actual == 1(bit) x 8(byte) x 1024(kilo) x 1024(mega) x 1024(giga)

(Edit: A formatted 160GB will report about 148GB in Windows, a 250GB will report about 233GB)

Second, what file system and cluster size are you using? With a 160GB drive and FAT32 for instance, your cluster size will be so big that files may take twice their actual size on the disk. In Windows you can check this by right clicking on a folder and comparing the difference between "Size" versus "Size on Disk"

Third, what are the size of hidden and system files. Pagefile.sys can be 1.5x your RAM if set to auto and Hyberfill.sys is the same size as your RAM. If you have, say, 2GB of RAM this comes out of 3.5GB of additional space. You may also want to check how much space System Restore is taking as it can take up to 12% of a physical volume.

Lastly, do a Defrag and see if there are a bunch of huge unmovable files or if your free space changes afterward.

 

[Sciberpunkt]

Yeah cluster size will play a big role. Copying a CD-ROM (~650MB) containing 40,000 tiny files less that 1K in size will easily claim more than 1GB of hard drive space due to cluster slack space. However, your scenario of a single 1GB file taking 2GB of free space isn't consistent with this theory. The only way we'll know for sure is if you give us actual numbers rather than speculative ones (# of files, avg. file size, free space before and after file transfer). The BIOS limitation only applies if your computer is relatively ancient.