Why get files changed when copied to external USB drive?

Question

I connected an external USB drive to my computer. According to dmesg it is:

scsi 4:0:0:0: Direct-Access     DMI      WD10EARS-00Y5B1  1.00 PQ: 0 ANSI: 4

The case says its a Sharkoon Rapid Case eSATA, but the drive itself seems to be a Western Digital 1TB. I want to copy some files to it and used Windows XP as well as a GNU/Linux live CD. Within Windows I used the explorer to copy the files and with Linux I used Nautilus or cp -r .... When I checked the copy I realised that some images look strange. I dug a bit further and used md5sum to compare original and copy. According to that some files on the USB drive had different hashes. When I tried copying again some files were different again, but some, which were different before, had the same content (and md5sum) as the original file. I have no idea, where to look for a solution. Have you encountered such problems? What can I do to circumvent it?

Answer 1

As this happens on both Windows & linux, I suspect there is a hardware issue, either with the USB-to-SATA controler in the case, or with the HDD itself.

Answer 2

Instead of the cp command you could use the rsync command. I'm not really sure what the issue, but from rsync's man file:

rsync always verifies that each transferred file was correctly reconstructed on the receiving side by checking a whole-file checksum that is generated as the file is transferred