Microsoft → Anyone else getting this "Size on Disk" Anomaly?

So I was checking some file sizes on my PC and noticed that when I checked the properties on a file or folder on my local drive, the "File size" and the "Size on disk" would either be the same or very close to being the same.

I then checked files stored on my Synology Nas on the network and the sizes are grossly different. No, I mean like night and day different.


WTH?

This should explain it for you.

»tinyurl.com/mue7cal

Blob

Yeah, I checked that out prior to posting. My question is why does windows 7 and windows 8.1 behave differently with file sizes on the network.

Is there a difference in allocation unit size between the two OSs?

Blob

I was under the impression that by default the two OS would have the same allocation unit size.

That is my assumption also.

Blob

Just verified it with chkdsk . They both have the same file allocation unit size.

Its funny, we just got new Windows 8.1 PC's at the job and when I checked the files on the NAS at work I get the same results as my home system with the outrageous "size on disk" numbers.

The file system on the disk is the thing that 'has' the allocation size. It travels with the disk; it cannot be different between two different operating systems.

So, the thing that controls the allocation unit size of files on the NAS is... the NAS.

However, despite allocation size, it's perfectly possible for an program to decide it's sensible to store 1 byte of data in a 53 gigabyte file. This is not an allocation unit size issue, it's just over-allocation of space on a particular file. That is probably not happening, but it could be.

I suppose I should point out that directories (folders) on Windows don't actually 'have' sizes -- that is, the size of a directory itself is always reported (at the program level) as 0. Explorer adds up the sizes of everything in the directory, recursively, and says that's the size of the folder.

Other operating systems, such as the Linux system (I guess) running on the NAS do have directory sizes. Though I don't see how that could affect anything here.

It's possible that the NAS is bungling the protocol that is used to report the sizes of files. Due to ancient history, it's a mess. Perhaps the NASes have different firmware and one of them has a bug fixed.

I'd look at indvidual files in the directory and see whether there are radical per-file differences.

I'd also run a network sniffer (Network Monitor, Wireshark) to see what's coming across the wire: this would absolutely determine who was at fault.

Check it with TreeSize and see what's going on.

Yes the NAS is what controls the allocation unit size on the NAS but my quandary is why would Win7 and Win8.1 get different results when they both have the same file allocation unit size.


Windows 8.1

I can't duplicate that issue on my Windows 8.1 system for files stored on a WHS v1 box.

First, let's squash this line of argument. The OS does not have an 'allocation size'.

If you look, for example, at the allocation unit size for C:, then what you've got is the allocation unit size for C:, and not for any other file system volume on the same computer, must less for any volume on the other sode of a network link.

So, if we are talking about the same file system volume on the same NAS device, there's only one 'allocation unit size' involved - the one on the disk in question.

--
My guess is that it's more likely to be a NAS protocol incompatibility. But that's probably because I used to work in that area, and know how many ways it can be got wrong.

Perhaps the NAS doesn't send a size-on-disk and therefore the client 'guesses' differently.

Two requests:

1. Can you post screen shots for the properties of a single file in that folder? (From both Win7 and Win8 if possible)

2. Any chance of installing Wireshark on the Win8 system and capturing traffic to the NAS when you're getting that size info?

I'm totally at sea with Wireshark so I'll try a capture with it and sent you the file via IM.

Screen shots of file posted


Windows 7

Capture file.

1.5tb slack? for 7 files. That can't be it.

OK, here's the relevant part of a response to a query for 'standard info' for the file
Peachpit.Press.The.Photoshop.CS5.Pocket.Guide.May.2010.pdf
which is in your screen shot above.

        
   QUERY_PATH_INFO Data
            Allocation Size: 268435456
            End Of File: 5686822
            Link Count: 1
            Delete Pending: Normal, no pending delete (0)
            Is Directory: This is NOT a directory (0)
            Unknown Data: 0000
 

Size around 5M, allocation 256M.

This is what the NAS server is saying. The Windows system is apparently innocent in all this.

Later at frame 158 the client needs to actually open the file. Here's the response. The size data are identical -- i.e., it's not just a buggered-up message. As far as we can tell, the file really has that allocation on the NAS.

    NT Create AndX Response (0xa2)
        Word Count (WCT): 42
        AndXCommand: No further commands (0xff)
        Reserved: 00
        AndXOffset: 0
        Oplock level: Batch oplock granted (2)
        FID: 0x4fe6 (\Manuals\photoshop tutorials pdf\Peachpit.Press.The.Photoshop.CS5.Pocket.Guide.May.2010.pdf)
        Create action: The file existed and was opened (1)
        Created: Jan  1, 2013 11:52:15.999999900
        Last Access: Dec  7, 2013 17:48:15.999999900
        Last Write: Dec 22, 2012 11:30:36.999999900
        Change: Dec 22, 2012 11:30:36.999999900
        File Attributes: 0x00000020
        Allocation Size: 268435456
        End Of File: 5686822
        File Type: Disk file or directory (0)
        IPC State: 0x0007
        Is Directory: This is NOT a directory (0)
        Byte Count (BCC): 0
 

So why are the results from the two systems so different?

Do you want to get the same sort of trace from the Windows 7 system?

Capture from Win7

That has exactly the same sort of response messages with the same size fields.

So, the NAS is consistently saying '5MB written, 256MB on disk' but for some reason Windows 7 doesn't believe it.

I see that I'm not alone, there are about two to three topics in the Synology forums about this, but no solution yet either.

I'm not familiar with the Synology NAS, is there any way to find out what the local file system thinks of the file?

Something like the Linux 'stat' command on the file would be good. That requires you to be able to get to a shell, though.