Is verifying a MD5 sum after copying 100GB of data safe?

I'm copying 100GB from a Windows 7 workstation to 2 external drives (if you have only one backup, then you have none). All files have a MD5 checksum. I've verified all MD5 checksums on the external disks after the copy, and they were all correct.

I have a D:\ partition that holds all files I want to backup: mp3, documents, videos, etc. I'm moving to a mac, so software preferences aren't needed. My bookmarks are at delicious.com.

My question is: is this really a safe approach to avoid incorrect copies or corrupted files on my external disks? I'm going to format the machine and give it away to my brother, so I copied all files this way.

Solution 1:

If the checksums match then you are near a 100% safe the files were copied correctly, provided the external drive does not fail.

Solution 2:

There is no 100% guarantee that the target and the source will be exactly the same. However, it the hash values match, the possibility of a corrupted file is very very low. It also depends on the length of the hash value. SHA is twice larger than MD5. So using SHA will be much more safe than MD5. I know an application called HashCopy. It supports both MD5 and SHA and automatically verify the hash values. It can be downloaded from www.jdxsoftware.org.