My computer's gone HAL on me!

May 6, 2008 5:45 AM

It appears that chkdsk has corrupted some of my files. How can I stop this happening?

I restarted my computer one day (just to refresh it, not because of an update, new program or crash) and it ran chkdsk automatically, which I thought was strange.

It found several errors in a folder of music I have in My Documents. It said it fixed them so I thought nothing of it, until a couple of days later I was looking over my backup logs and my backup program (JungleDisk) had noticed that some of my music files had been modified, so had made copies of them. The files were the same ones chkdsk had scanned and "fixed" a few days before. I thought I'd better check out the files, so I went to the folder (whose name was corrupted btw) and tried to play them...but although the files still showed the correct size, they wouldn't play! They were corrupt!

This has really shaken my confidence in my PC. I am running Win XP Home with NTFS. I have a large music collection, and am left wondering: why these files corrupted? how many MP3s and other files have I lost without realising?

Can anybody offer an explanation of the problem? Is there anything I can do to stop this happening again?

posted by edbyford to computers & internet (9 comments total)

It's more likely that something else caused those files to be corrupted, such as a power-off or a write failure, and chkdsk ran to fix those errors. Chkdsk just fixes corrupted filesystems though, it can't fix everything. It can for example fix a corrupted file header, but if your computer accidently writes over a MP3 file with garbage data, it won't have any way of getting the old data back. Hard drives fail, sometimes losing some or all of the data stored on them, and the only thing you can do is backup the data somewhere else.

Other than backing up regularly (which you are already doing), you might want to start making SFV files for your music. You can run those files to find out if your music files have changed in any way, so that you can download them rip them from the original CDs that you legally purchased.
posted by burnmp3s at 6:12 AM on May 6, 2008

Do you keep your data on a separate drive / partition from your main operating system volume (typically C:)? I prefer using an entirely separate physical drive, which is of course backed up to an external drive: this is a typical practice that may help prevent corruption and prevent wear and tear on the drive caused by the sheer amount of constant read-write activity that occurs on your primary volume.

RAID might help -- in my organization we use RAID everywhere, and use separate physical volumes for the operating system vs. data, but I am not particularly in favor of software-based SATA RAID. I haven't dealt with it a whole heckuva lot, but my experience with SATA RAID NAS devices has been sketchy.

It's grrreat that your backup program caught this for you -- I would want to research that product and determine whether it uses checksums (good) or less reliable heuristics (like checking the modify date -- bad) to determine if a file has been modified. The important thing is that you are making backups, and are able to check integrity, so that ideally you won't run into a situation where you back up corrupted data and overwrite all of your backups with garbage.

Personally, I haven't been using a backup program at home and rely on my own baling-wire methods, and this reminds me that I need to be more careful and find a real solution.

The greater problem is that no single form of media is 100% reliable, no operating system is 100% reliable, and so forth.

I like the idea of having checksums immediately -- the second I create an MP3, I want a fingerprint that I can compare against later.

I've tinkered around with building my own MP3 "operating system / shell" and this is a feature I would definitely want to incorporate when I rewrite it down the road ;)
posted by aydeejones at 7:29 AM on May 6, 2008

Most likely those files were corrupt before chkdsk ran. It found an inconsistency in the file system and tried to fix it.

In fact, we dont know why it ran. Did the power go off that night? Did it lock up?

First link on google for disable chkdsk. I highly recommend against this, but its your computer.
posted by damn dirty ape at 7:34 AM on May 6, 2008

RAID might help -- in my organization we use RAID everywhere, and use separate physical volumes for the operating system vs. data, but I am not particularly in favor of software-based SATA RAID. I haven't dealt with it a whole heckuva lot, but my experience with SATA RAID NAS devices has been sketchy.

One thing to point out is that RAID is not a backup solution. Some levels of RAID make it more easy to recover from drive failures, but you still need to backup your disks.
posted by sbutler at 7:43 AM on May 6, 2008

Are you using Itunes by any chance? It somewhat (not frequently but enough so I know) often deletes music tracks from my hard drive for no reason. They just dissapear though, they dont' seem to be corrupted, they're just gonzo. I've had this corroborated by other users. I recently stopped having Itunes "manage my library". Not sure if this is helping or not.

Just a thought. It only happens with music files. I blame Itunes (for windoze).
posted by sully75 at 7:58 AM on May 6, 2008

Windows will run chkdsk if it hasn't been shut down cleanly. If you did that restart by jabbing it in the guts with a front-panel Reset button, as opposed to using Start->Shut Down->Restart, it wouldn't have shut down cleanly. If Windows shuts down uncleanly, files may well get corrupted. This happens less often with NTFS than with any of the FAT variants, but it does still happen.
posted by flabdablet at 8:25 AM on May 6, 2008

Also its worth mentioning that if your files keep getting corrupt for no reason then it might be time to start thinking about replacing the drive. If the chkdsk reported a bad sector or bad block then the first thing you should do today after work is back everything up and invest in a new drive.
posted by damn dirty ape at 9:01 AM on May 6, 2008

Yeah, you're blaming the paramedics for your broken leg. They just tried to splint it, that's all.

CHKDSK should not run unless something triggers it, such as the root directory getting corrupted. When it runs, it doesn't actually muck around with files directly. What it does is correct directory (folder) sectors. These are filenames with pointers to file locations on the disk. It will happily "correct" these folders, making them "uncorrupted", by pointing your filename to utter garbage. The file length will be "corrected" by extending the file into garbage sectors to match the correct length. With NTFS there's a less chance of this happening than with FAT, but it still can happen.

The point is that CHKDSK is designed to save your ass by fixing minor errors that would prevent you from booting. It isn't designed to save all your files. You'll need Norton or another disk utility for that -- and good backups, of course.
posted by dhartung at 10:37 AM on May 6, 2008

Thanks everyone! I am now making checksums on my files using QuickSFV, a program suggested by burnmp3s!
posted by edbyford at 3:19 AM on May 7, 2008