Files in subfolders disappear from pen drive

[Mark P]

I've a 512MB pen drive and have been having strange problems with it. Whenever I copy whole folders on to it, the files are there until I remove the drive (or restart the computer with the drive still plugged in), and then the folder remains, but it's empty. The really strange thing is that pre-existing folders still contain their files, and that files copied onto the root of the pen drive don't disappear. I've tried various manipulations to make sure that everything is written to the drive before I remove it, and I've confirmed the files really are there on the drive in the first place by opening them directly from the pen as soon as I've copied them. Thinking it sounded like a FAT problem I reformatted the pen, and now it seems to be working OK, BUT I was wondering if anyone else had experienced these sorts of problems. In particular I did not experience this issue until I had a lot of files in a lot of folders, so I wondered if the FAT can get full if it's stored in a dedicated, limited part of the pen. Things that count against this are the fact that when I deleted a number of folders, the problem persisted until I reformatted the drive, and that there has never been a problem with files on the root of the drive.

this was an ebay purchase, from a UK seller but the manufacturer is an obscure chinese outfit, so my chances of redress are slim - if I can understand what's going wrong I hope to be able to work within those limitations rather than consigning it to the scrapheap.

Thanks

[JohnGray]

What operating system are you using?
For XP the pen drive/USB flash drive doesn't need a driver,
but for Windows 98 it does. These drivers differ depending on the manufacturer of the pen drive (and are mutually incompatible, in my experience...) -- and even two different capacity drives (in my case 128 MB and 32 MB) from the same manufacturer can cause problems if one is inserted after the other without an intervening restart!

Your FAT table should not have the problems you describe, since there are always suffficient entries for the disk capacity. The only problem I can think of is if you have more than 510 (or so) subdirectories or file names in the root directory -- but you'd get a message for that.

Have you run SCANDISK or CHKDISK (as appropriate to your operating system) on the drive? This may show up that you have removed the drive before the directory or files have been written properly.. (Not unusual with 3

[cbaldrey]

I've experienced similar problems myself. I think I have it down to pulling the pen drive out, before "ejecting" or stopping the pen drive via the taskbar.

It seems (in my cases) that whatever is written to the drive in a session, is there until I pull the drive out, unless I eject it first.

[jhelfer]

There is a limit to the number of files (and directories count against this limit to!) that can be stored in the root directory. Looks like 512 fo FAT 32. I think this depends on the sector size used by the disk. If you were to format with FAT 16, I believe the number would be lower.

But anyway, in my experience, it seems like some of these flash devices (pen drives and memory cards) do have a tendency to corrupt files, especially as they are inserted and removed often. I guess it's to be expected, since it is just FAT. It's not really very resillient.

Just use chkdsk and chkdsk /f and you should be able to recover lost files (as file0000.chk files, which can be renamed).

[Mark P]

Thanks for the thoughts. I've only used it on winxp and 2000, never pull it out without going through the "safely remove" process or shutting the system down first, and have only one level of subdirectories.

So looks like it's just crappy hardware then. Though it's still odd - I could understand crappy hardware corrupting the odd file, but this consistent behaviour of retaining files copied to root, but randomly dropping the entire contents of subdirectories whilst keeping the directory structure hinted at something more systematic.

I'd not thought of using chkdsk on the pen though, I'll try that in future.

cheers