Will CHKDSK corrupt files.
No, it won't. Hi, everyone.
Leo Notenboom here for AskLeo.com. I'll explain that,
of course, but let's first get to the question that prompted this.
I recently did a CHKDSK scan on two hard drives with video files.
The first scanned with no options checked.
It did not show any details of progress except the progress bar.
It got to the end and then froze, although the computer did not freeze.
And the only way to exit it was to shut down the computer or reset.
Do you think any of my video files got
corrupted or changed in any way with the other hard drive?
I scanned four times without errors.
On the fifth time, I scanned it on another
computer, and it said that it had a file system error.
Needless to say, I did not fix that.
I don't know if one of the four times
before I had checked any options, but I'm thinking I had nothing clicked.
Is it possible that my video files on the hard drive got corrupted or changed
in any way, even if I had clicked one or both of the options?
You may have problems with your video files, but CHKDSK did not cause them.
I think that's really important to underlie here.
CHKDSK is an analysis and repair tool.
Much like an investigative journalist, its job is to expose corruption.
It doesn't create corruption.
But unlike an investigative journalist,
CHKDSK, with the appropriate options selected, will try to fix things that can
actually result in some side effects that look like corruption but in fact aren't
anything new on the hard disk.
CHKDSK's job is to examine all of the files and folders on your hard disk
and make sure that all of the overhead information that lets Windows determine
exactly where files are on the hard disk is all correct.
It's all stored properly, is all internally consistent.
That's its job.
That's the only thing that it is really all about.
And it's one of those things that pays
attention to the difference between, say, a Fat 32 file system,
which gets checked one way for certain things, and an NTFS file system,
which gets checked a different way for certain things.
Now, CHKDSK without any options,
and I'm talking specifically here about the command line version.
CHKDSK does not do anything other than read.
It's a read only operation.
If it reports errors, those errors were there already.
Those errors were there before you ran CHKDSK.
It's just telling you that there's a problem here.
Exactly how severe the problem is or which files are affected is beyond
the scope of what it's going to tell you, but it's at least going to tell you that,
hey, we found some problems with the file system here.
You might want to consider fixing it.
That's a good time, by the way, to do a backup right then and there.
Before you let CHKDSK try and fix anything.
You'll understand why in a moment when you specify either the F or the R
option and R really just implies the F option.
It's the fix option.
When you specify F, CHKDSK, then when it determines that there's
a problem on your hard disk, we'll try to make some changes
to the information on the hard disk to repair things.
It may recover files.
It may make sure that directory listings are consistent.
There may be some fragments of files
that it can't associate with other things that it doesn't know where they belong.
So it will actually make the data
for those things available through files that it creates.
But the important thing to realize here is
that when CHKDSK tries to fix a problem, it is not creating a problem.
The problem was already there.
The corruption was already there.
CHKDSK is either just reporting it or trying to fix it.
The reason that it's sometimes easy
to think that CHKDSKmay have caused a problem is that CHKDSK may cause
an existing problem to manifest in a different way.
The most common scenario is if you have a problem on your hard disk that you don't
notice, you just don't know that there's a problem.
You run CHKDSK, it tells you that there are issues with the file system.
You run CHKDSK again with the /F option and it fixes them.
And now all of a sudden things don't work quite right.
The problem was already there.
How it was exposed has changed.
What's different is that before writing
CHKDSK with the fixed operation there was a logical problem on the hard disk.
The information about the file system was incorrect.
CHKDSK fixed it.
That fix then may manifest in another way.
The file system is now internally consistent.
Everything, all the information about
where the files and folders are on your hard disk is correct.
But as a result of fixing this, as a result of making the file system
internally consistent, the problem that you had,
the problem that you already had may manifest in a different way.
That's why I say one of the things you
might consider doing when CHKDSK reports there to be problems on your hard
disk is to run a backup right then and there.
Now, the backup may fail depending on the kind of backup you're doing.
If you could do an image backup, do it.
If you can't do an image backup, do a files and folders backup.
Do something to back up the information on that hard disk.
Run Check Disk /F or /F /R and then potentially do the backup again.
Do another backup so that you're getting all of the information you possibly can.
You may not get the same information in the two different backups.
The existing corruption on the hard disk may prevent you from getting some things
and then the repair may prevent you from getting some other things.
But the problem fundamentally was there all along.
CHKDSK didn't add anything.
CHKDSK simply changed potentially how the error manifested.
Where do errors come from?
Well, that's a really hard one to answer.
There are a number of I'll just call them common scenarios.
Hard disks. They are hardware.
They are subject to hardware failures.
It can happen.
SSDs, for example, wear out.
One of the ways an SSD or a thumb drive
might manifest as having worn out is CHKDSK failing.
It's being unable to correctly store the file system information.
Typically, when flash memory and SSDs or
thumb drives dies, it dies a little bit more catastrophic than that.
But this is one way.
Another way is if you've got a laptop or
a hard disk, an old style hard disk with spinning platters and you drop it,
that can cause physical damage within the hard disk.
The other scenario that maybe is the more common one it's become less common because
of some changes in Windows over the recent years.
But the other scenario is this is the big one, the way we used to recommend.
You never ever unplug a USB hard drive
without doing first safely remove hardware.
That safely remove is all about making
sure that the file system has been completely and safely rewritten or written
to the hard disk and is internally consistent.
If you unplug the hard disk before
that has allowed to complete, then you may end up with check disk errors
that will manifest at some point in the future.
Hope that was helpful.
For updates, for comments,
for links related to this topic and more, visit askleo.com/8425.
I'm Leo Notenboom, and this is Askleo.com.
Thanks for watching.