Empty files :O

[commodore]

I was looking for some photos on my disk, and came across several files that were literally empty. Attributes such as file name, size, date, icon... seem just fine, but there is no content whatsoever in the file. It was quite a shock. I think it might have happened when I was migrating all the data from one disk to another (via an external USB backup disk). I don't recall any errors being issued.
The empty files are sort of sequential: (first) 90 % of files in one folder, all the files in the folder which is alphabetically before this one, and last couple of files in the folder before this second one.
Any speculation on what might have caused this? And, most of all, how to avoid it in the future and how to ensure data integrity when performing backups or migrations of large quantities of files/data? I'm using TC 7.56A.
It should be OK once I locate the CD which hopefully still contains all the photos, though. But I'm not sure anymore whether any of migrations didn't damage any other files along the way.

[Hacker]

commodore,

files that were literally empty

What does that exactly mean?

Roman

[petermad]

Maybe the files were already "empty" (does that mean 0-byte length ?) before they were migrated.

[csmarshall]

I was looking for some photos on my disk, and came across several files that were literally empty. ...
Any speculation on what might have caused this? And, most of all, how to avoid it in the future and how to ensure data integrity when performing backups or migrations of large quantities of files/data?

If you are talking about JPG files: that image format is prone to failure in various situations. Depending on which image browser one uses, the first thing one really notices is either a partially scrambled image -or- a seemingly 'blank' image. I say 'seemingly blank' as the raw bitplane data is still there (filesize itself is left untouched), but it is so badly damaged that the image reader code malfunctions and stops displaying.

I have a constant fluctiation through roughly 1 TB of images (TIF, BMP and JPG) in around 50 folders at any given time and constantly lose a few JPG images, regardless of which OS or drives I use. Following a few tests with intentionally damaged files it seems that a single corrupted JPG screws up the copying process, "carrying" damage into other files - something I never thought possible. It might be a technical misunderstanding on my part, but that is what I perceived. In short: if one file is (for whatever reason) corrupt and part of a copy batch the chances are high that following files will also become corrupt.

I am no techie, so I was never able to get behind it "in depth". But ever since I nearly lost the pictures of my kids, I switched to storing all vital pictures as TIF images - with success, it seems, as all pictures stored that way have remained intact even after years and dozend of copies.

[commodore]

By "literally empty" I mean they have no data within the file (I'm not talking about the distorted bottom part of a JPG image, which I also encountered on occasions).
The file itself seems OK on the outside: e.g. DSC00411.JPG, size 833653 bytes - so nothing to suspect until you actually try to view them. As they didn't show any images in either Explorer previews or in ACDSee, I opened them with TC's Lister. No matter which encoding I chose, there was nothing in them. If I open them in Notepad++, they're filled with NULL characters.

The image viewers have nothing to do with this, as I always use TC for copying data (either F5, F6, or Synchronize Dirs, depending on the situation). And the photos in question were OK last time we looked them (which might be a year or so ago). No bad sectors or chkdsk errors in the meantime, though.

[MVV]

filled with NULL characters.

So, it is the correct description of your 'literally empty' files. BTW, you can see the same in Lister using HEX view mode (NULL characters are bytes with hex value 00).

Null-filled file is a file which space was allocated but not filled. I don't know all ways to get such files but the one of them is that OS weren't shut down correctly and OS cache wasn't flushed just after copying files.

[theosdikaios]

NULL filled files can be caused in TC copy method. See here
http://ghisler.ch/board/viewtopic.php?p=218141#218141

[commodore]

I'm using the default settings for Copy/Delete - i.e. "Use standard copy method (recommended)" is checked. According to Help, TC thus uses the default Windows method for copying files (same as Explorer, I suppose?).