Blu-ray drive shows the file sizes on the data disc incorrectly

Hi! I have a little project going on right now that involves burned 100gb blu-ray data discs.

I noticed today, when I compared the amount of files in the same disc in Windows and linux, that linux shows the file sizes and the number of files in the disc incorrectly.

When I select all the files inside the disc in the gnome’s file browser and select “properties”, I notice that gnome shows about 100ish more files in this particular disc compared to what windows showed.

Is this normal? I use Pioneer BDR-XS07TS external blu-ray drive. I have understood that this drive “should” work with linux, even though the drive’s original package never mentions anything about linux support.

The drive seems to work okay. This I mean that I’m able to play burned videos and other content without problem, but I’m a bit paranoid about how linux reads this discs and if it might actually pull these files incorrectly to my computer for future usage.


It seems that the number of items seem to add up with windows. I was not aware that gnome counts folders and files together as items, so I imagined that this gnome “number of items” was only about files and not about folders. Windows seems to show files and folders separately, while gnome counts files and folders together.

However, it seems that the folder sizes are different when I look at, for example, the size of one folder on disc in Windows. For example in windows one folder seems to be 300-400 megabytes smaller compared to what gnome shows. don’t know why this happends.

My linux computer also gave I/O ERROR and stopped the transfer completely, when i tried to copy one zip file from my DVD-R data disc using my Pioneer BLU-RAY drive to my computer’s internal SSD. Windows copies this particular zip file without any problems with the same blu-ray drive and with the same DVD-R disc. When I tried to copy this same zip file with my normal USB DVD drive from this DVD-R disc on my linux computer, it copied the zip file without any problems.

Maybe there is some kind of problem with linux’s optical drive drivers or something?

And, you know that Fedora is wrong and windows right because?

Hi! I used windows burning program called burnaware, which analyzed the disc and showed the same total amount of files as windows’s properties tab showed. So windows should show them correctly at least in theory. I have no idea why gnome shows it this way.

Hi. In practice you don’t have any tangible proof of windows being right. Actually, you don’t have a proof that gnome is right either.
Find a directory that shows the discrepancy and save the list of files. Then, compare the results.
Under linux it is easy within a terminal to obtain a list:
ls -laR directory > ~/list.txt
under windows: find a way.

When burning 100gb blu ray discs, you can add only something like 93.2GB of data to that disc. Other 6 gigs goes to the file system (UDF file system). When viewing in gnome’s file explorer (properties tab) it shows that this drive has 99.4gb of data in this particular blu-ray disc. That shouldn’t be possible. I don’t know why but this is what it says.

What filesystem are you using on the drive? Do you notice anything about the additional files?

I don’t know what Windows showing, but one thing of note: properties in GNOME Files shows Items, not files — and I just confirmed that that includes directories (subfolders) as well. Perhaps Windows is just actually counting files?

Can you elaborate on the difference in file sizes? I notice that GNOME FIles is reporting sizes with 1000-based metric prefixes, not 1024-based KiB or MiB.

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Are the units in gibibytes or gigabytes?

Here you are looking at the properties of the disc itself rather than a folder? I don’t have any optical media to test, but it looks like this is probably using the statfs() system call to query the filesystem for information. It wouldn’t shock me at all for this to be calculated slightly differently from on Windows.

II could concentrate on validating your data in a different way. rsync -c between your source and destination, that should give good confidence that everything is transferred correctly. (To be completely sure that nothing is cached but not written correctly, probably a good idea to remove the disc and re-insert it. But that shouldn’t even be necessary.)

Hi mattdm.

All my data discs are using UDF file system. When looking at some of the files, I can’t really see anything missing. but in the otjer hand, this disc has a lot of stuff in smaller chunks and there is a lot of individual files on that disc. So i can’t really check them all manually. Burnaware did analyze the disc and also reported that there is something like 92gb worth of files, which corresponded with windows’s file explorer.

Windows and burnaware shows that there is around 4411 FILES total. Gnome shows that the total amount of ITEMS is 4549. So basically 4411 files + 138 folders is 4549. So that seems to add up…

But the problem is how gnome shows the space. Gnome shows that the total amount in use on that disc is 99.4GB. I have little over 92.5GB of stuff on that disc. that 99.4GB just can’t be possible since you can only burn 93.2gb worth of files to one 100gb disc. So windows seems to report it correctly. Also when I copy one of the folders to my inernal ssd, it shows that the file is a lot bigger (something like 400-500mb bigger) compared to windows when I copy the same folder to my other computer which has windows installed.

Is it possible that GNOME is including the overhead, while Windows is not?

The file is a lot bigger, or the space used by the folder? This too could be accounted for by differences in overhead between filesystems. (Depending on the filesystem, this can be particularly true if you have lots of small files. Each may actually use a minimum size of 4096 bytes.)

It’s possible that something is wrong, but there are a lot of reasonable reasons for discrepancies of the kind we’re talking about. I again encourage you to use rsync to check the contents.

To do that, run:

rsync -ricn sourcedir/ destinationdir/

The options here are:

  • -rrecursive, so it goes through all subdirectories
  • -iitemize changes — tell what’s different (see below)
  • -c — don’t rely on file size and timestamp — do the slow thing and checksum each file
  • -n — dry run — no actual copying (so you can’t mess anything up)

If this comes back with nothing, the two directories have identical contents. If it lists files, they differ — and check under --itemize-changes in the rsync man page for the codes for this report will give for exactly what didn’t match.

I’m not sure if windows includes the overhead. It says that this particular folder uses 2.57GB on windows, but in gnome it says that this whole foler is something over 2.8GB.

The whole folder seems to use a lot more space according to gnome compared to my windlws computer. This might be because the somehow show the same folder’s size in different way or something.

I just noticed that when I use my blu-ray drive and copy one of the zip files from my normal DVD-R data disc, it complains something about I/O error and stops the copying from my DVD-r disc. When I use normal usb dvd drive (yes I have that too), it seems to copy that zip file normally with the same usb port. Maybe there is some issue with the driver?

Okay. Thanks for that command line. Today I don’t have time to try that out because I have other important stuff to do, so I might try it tomorrow.

There are a lot of parts that may not be considered.
A 3 TB disk drive only has 2.73 TiB space (units differences)
One app may report actual sizes and others may be based on sectors allocated. As noted above a minimum block size is 4096 bites which bloats the apparent size of a large number of smaller files.

Unless you have proof that one or the other is wrong the best thing is to recognize that there are differences and accept that as a fact.

The advertised size of a 100 GB bluray disk is in GigaBytes, not Gibibytes, which accounts for a noticable shrinkage at the start. 100 GB is actually 93.13 GiB.

I see. You might very well be right. It at least shows the number of items correctly if you add the amount of files and the amount of folders together.

I found a way to see the actual size on disc in windows. This particular folder I copied from blu-ray disc to windows computer uses 2 768 687 104 bytes (“size on the disc” in the windlws properties tab). The folder size is 2 762 677 856 bytes (simply “size” in windows’s properties tab). This is still less compared to gnome, which reports the folder’s size as 2.8gigabytes and a bit over. Can’t really tell if this is normal (gnome simply shows it in a different way) or if there is actually some kind of problem with linux’s oprical drive driver or something. This blu-ray drive also failed to copy zip file from DVD-R disc (gave some kind of I/O error and stopped copying it completely) when I tested it. With my other, normal usb DVD drive, this particular zip file was copied without any problems.

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Hi Villy. It seems that Windows and gnome shows the folder sizes in gigabytes. This is atleast the case with windows, but i’m not 100% sure about how gnome shows it. It appears that gnome also shows it in gigabytes…

Another factor is rounding. 2.762 is shown as 2.8 when rounded to a single decimal digit.

I’m not sure how aggressive gnome’s rounding is. If this is indeed the case, then it would be nice if gnome would show it more specifically so we can see accurate file size and how much space it takes from drive.

If you need more accurate numbers, it’s probably better to use a tool meant for the job — for a GUI, try the GNOME Disk Usage Analyzer. From the command line, look at the venerable df and du tools.