Does Windows calculate CRCs to check every file operation?

windows checksum data-integrity crc

6,182

Windows doesn't actually preform any redundancy on file transfers, this is a misnomer for the device driver accessing a bad sector block (see the SO question What, and where, is the NTFS CRC windows complains about? and this Microsoft KB article; NTFS does not store any kind of file checksums). If you receive this error on your computer, you should ensure your hard disk's integrity (and possibly invoke chkdsk with the /r flag).

Long story short, Windows does not verify any files after they are transferred. You can use another software tool like TeraCopy to verify data after moving/copying files.

6,182

bwDraco

I'm a computer and tech enthusiast with a variety of interests ranging from video games to fountain pens. I stand behind everything I post here. If you find any problems with my posts, feel free to leave comments, edit them, or let me know in chat if you have any questions or concerns. If you're curious about my answering style, it's inspired by the answers posted by Thaddeus Howze ♦ at Science Fiction & Fantasy. This chat transcript details why I made this change. I'm also one of the resident spam fighters on Super User and can catch spam others miss. If you suspect that one or more posts are spam, bring it up in the Ask a Super User Moderator chat room, and be sure to ping me—I'm around most of the time. Don't forget to flag blatant spam—it takes just six spam flags from the community to delete it. It sounds like flagging posts as spam isn't enough; they need to be flagged specifically to your attention (and what are the odds that you haven't already found it). —fixer1234 (source) If you're wondering about my name, it used to be DragonLord, but I've had to change it due to a bizarre trademark dispute. Feel free to call me Draco or by my real first name Brian. As an aside, I'm a bit of a photo enthusiast. I shoot with Pentax eqiuipment, and you can find me on Pentax Forums.

Updated on September 18, 2022

Comments

bwDraco over 1 year

When Windows encounters a file corruption on a file system, it may return the following error message:

Data error (cyclic redundancy check).

This suggests Windows checks every file operation (copy, move, etc.) by calculating CRCs. Does Windows really do this, whether during or after the operation?
- Admin about 2 years
  
  See also superuser.com/questions/1719053/…
bwDraco about 11 years

I've actually looked at the linked Stack Overflow question. What I'm asking is whether Windows calculates CRCs on the fly during file operations, not necessarily whether it stores them.
Breakthrough about 11 years

@DragonLord I do not believe it does, otherwise these errors would appear during normal read/write errors where there are not bad sectors reported. You can use a third-party utility to actually verify file contents once they are transferred.
bwDraco about 11 years

Edited the question to clarify. Does Windows perform any error checking while a file operation is in progress?
Breakthrough about 11 years

@DragonLord in my experience, no. I have used Windows to copy files to bad drives before, and sometimes have not received the error message. They were only detected when I manually tried to verify the CRC (or MD5/SHA1 hash) of the files and they did not match. I believe the error message is only shown when the actual disk device driver throws an error during transfer, or the NTFS filesystem itself detects some kind of corruption.
David Schwartz about 11 years

There are actually three distinct conditions that can cause this error (in the typical IDE/SATA interface to conventional hard drive): 1) Data corruption on the connection between the hard drive and the controller. 2) Data corruption in the data read by the disk controller from the disk surface despite retries. 3) Access to a disk sector known bad by the controller that cannot be remapped until written to.