I’m confused by the disk usage figures on 2 x 250 gb disks.

Avoriaz

This isn’t a problem as such, I would just like to understand what is going on.

I have two disks that I use for backing up my files. One is a Maxtor and one is a Samsung. Both are nominally 250 gb capacity.

I store exactly the same data on each, yet one appears to need about 3.5 gb more to store exactly the same data. Both are formatted for NTFS with the same cluster size.

I currently have 164gb of data stored on each disk. If I select all folders and click properties, both disks show exactly the same figures.

Size 164 GB (176,833,783,363 bytes)

Size on disk 164 GB (177,110,204,416 bytes)

But if I click “Properties” on the disk itself, I get these figures, and they are significantly different on the two disks.

.............Samsung................................ Maxtor

capacity 232gb 250,056,704,000 ..........233gb 250,994,384,896
used .....165gb 177,639,915,520 ..........168gb 181,222,531,072
free space 67.4gb 72,416,788,480 ........64.9gb 69,771,853,824

The Maxtor disk has a slightly higher actual capacity but appears to need about 3.5 gb more to store exactly the same amount of data.

The only other things on the disks are the Recycler and System Volume Information system folders. The Recycler is empty and presumably the SVI folder will be fairly small and of similar sizes on each disk.

Why does the Maxtor need that extra 3.5 gb?

The only thing I can think of is that maybe there is 3.5 gb of bad sectors on the Maxtor that is being shown as used space.

Any technical experts care to offer an opinion.

PS, why does the Maxtor have a higher actual capacity? Are 250gb disks not made to an exact standard but vary a little between makes and models?

bookduck

although each drive is the same size, the bios will probably see the two dissimilar different, but think 3gig different is quite a bit. 3 gig in corrupt sectors would be a bit worrying. On my 500 gig drive i've 45gig missing

This is the first thing I do

I'd go to a dos prompt, then on each drive, type dir /s /a at the bottom it tells you the total no of files and directories listed

Second thing, to be sure, I'd go to a dos prompt, then on each drive, type cd \, then attrib *.* /s > avorias.txt

This should give you a list of all the files on your pc. Then I would compare the two avorias.txt files by at the dos prompt using comp or fc - can't remember the difference any more except comp did not need switches

It could be that your system has been compromised - root kit hidden files too? Swap file? Log files? are also suspect.

It could be that your backup strategy is not backing up locked files?

sjrinteriors

Hi

is this system on a RAID? Mirrored array maybe!

What you will find is that the O/S is on one drive but not the other, hence the difference in storage capacity..

Avoriaz

Thanks for the replies above. I should have given more details.

I have a laptop with an internal 80gb disk. That contains my OS, system files, application software, personal files etc.

The two 250g disks are both in external USB connected caddies. They do not contain any OS, system files, restore files etc other than Recycler and SVI. They are used solely for storing music video files. I record music videos, concerts etc on Sky and download music files from the internet. I have about 900 of these music files. They are mainly mpg and avi files plus a few other formats. Obviously I cannot fit 165gb on my 80gb laptop drive so I bought the two disks for video storage. Each contains the identical files in case one fails.

I play the videos on a music server connected to my TV and HI Fi or on the laptop.

I am as sure as I can be that the disks not affected by any virus or malware etc. I am very thorough with my precautions and I have AVG anti virus, a decent firewall and I run spyware and virus checkers regularly. I have never knowingly had a virus related problem. There are no executable files on these disks and I am not aware that mpg or avi files can carry a virus or trojan etc.

I back up manually. I have a third 200 gb USB external disk that I use for my regular back ups.

The 250gb disks are only occasionally connected to the laptop vis USB when I want to put new files on them or copy some to play on the laptop.

I should stress that I don’t actually have a problem. The disks work fine and the laptop works fine.

I was just curious why one disk uses 3.5 gb more than the other to do the same thing. That just struck me as curious.

mdbarber

Not counting the usual bumph from drive manufacturers counting a megabyte as 1000 kilobytes, ooo the robbers
Having never gone into filing systems at theoretical level, i can't give you a definite answer but from a practical point of view. there may be two causes
1 The actual size of files is very difficult to read, due to some of the space being "potential" ie all digital data is ones and zeroes (how much is 150million x zero)
2. the alternate data stream(ads) used in ntfs filesystems, which is not counted as part of a file size declaration but still requires occupation of disk data space potential
not much to worry about really, in fact 5% i would say is pretty average for any sort of file system over head
hth's

ooo i almost forgot cluster sizes as well, how could i?, clusters are the minimum storage space on a disk so a 1k file using 4k cluster equals 4 k usage this also applies to parts of files so using 4k clusters 41k file uses 11 clusters ie 44k

fwor

Is it possible that one of these drives has a hidden restore partition on it from a previous life in another PC?

I don't think the reason can be bad sectors because (IIRC) all modern drives have spare unused sectors above the nominal capacity which are reserved to replace bad ones.

One thing that may shed more light on things: Try using a good partition editor such as GPARTED to see if there are any oddities in the partitioning of one of the two drives. It comes as standard on most Linux LiveCDs (i.e. you don't have to install Linux to use it), or you can get it in a smaller ISO on System Rescue CD:

http://www.sysresccd.org/Main_Page

This ISO also has some other very useful system recovery tools on it, such as Partimage, Test-disk and the ability to read and write to NTFS disks, along with just about any other file system format.

Avoriaz

fwor wrote: »

Is it possible that one of these drives has a hidden restore partition on it from a previous life in another PC?.

I suppose it is possible although I did fully format both disks without multiple partitions when I started using them for their current purpose.

I will check in "Manage" next time I use them.

As I don't have an actual problem, I should probably just stop thinking about it and start spending more time watching the actual videos.