Files corrupted on transfers?

  • Thread starter Thread starter Mobius
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Mobius

We have backed up files and folders routinely innumerable times over the
years for working systems to external drives - mostly USB. These back-ups
have come in might useful a few times!

Sometimes we find that some files on the external drive give a 'corrupt' or
'crc' or 'damaged' error when tried to be opened. This happens randomly and
for any file type - exe, doc, html, iso or other.

On a rough average we estimated that about a couple of percent of all such
back up files are thus unusable. While no critical files have been 'lost' so
far - we always have two separate back-ups of everything - it still is
interesting. Because no two identical file on both back-ups appear unusable
at the same time - at least so far.

Just wondering - what might be the possible cause/causes - and what might be
done to ensure better transfers. So far we use either a manual 'copy' in
Windows Explorer or sometimes a file-sync utility like SmartSync Pro.

Regards and thanks for any insights.

Mobius
--------
 
Mobius said:
We have backed up files and folders routinely innumerable times over the
years for working systems to external drives - mostly USB. These back-ups
have come in might useful a few times!

Sometimes we find that some files on the external drive give a 'corrupt'
or
'crc' or 'damaged' error when tried to be opened. This happens randomly
and
for any file type - exe, doc, html, iso or other.

On a rough average we estimated that about a couple of percent of all such
back up files are thus unusable. While no critical files have been 'lost'
so
far - we always have two separate back-ups of everything - it still is
interesting. Because no two identical file on both back-ups appear
unusable
at the same time - at least so far.

Just wondering - what might be the possible cause/causes - and what might
be
done to ensure better transfers. So far we use either a manual 'copy' in
Windows Explorer or sometimes a file-sync utility like SmartSync Pro.

Regards and thanks for any insights.

Mobius
--------
Click to expand...

CRC (Cyclic Redundancy Check) errors are bad news. They occur when Windows
is unable to read data from the storage medium. They invariably point to a
hardware problem.
 
We have backed up files and folders routinely innumerable times over the
years for working systems to external drives - mostly USB. These back-ups
have come in might useful a few times!

Sometimes we find that some files on the external drive give a 'corrupt' or
'crc' or 'damaged' error when tried to be opened. This happens randomly and
for any file type - exe, doc, html, iso or other.

On a rough average we estimated that about a couple of percent of all such
back up files are thus unusable. While no critical files have been 'lost'so
far - we always have two separate back-ups of everything - it still is
interesting. Because no two identical file on both back-ups appear unusable
at the same time - at least so far.

Just wondering - what might be the possible cause/causes - and what mightbe
done to ensure better transfers. So far we use either a manual 'copy' in
Windows Explorer or sometimes a file-sync utility like SmartSync Pro.

Regards and thanks for any insights.

Mobius
--------
Click to expand...

As Pegasus suggested, your error might be hardware related. You
should consider replacing the "affected" hard drive and get the older
drive checked out with the drive manufacturer's diagnostic tools.
 
We have backed up files and folders routinely innumerable times over the
years for working systems to external drives - mostly USB. These back-ups
have come in might useful a few times!

Sometimes we find that some files on the external drive give a 'corrupt' or
'crc' or 'damaged' error when tried to be opened. This happens randomly and
for any file type - exe, doc, html, iso or other.

On a rough average we estimated that about a couple of percent of all such
back up files are thus unusable. While no critical files have been 'lost' so
far - we always have two separate back-ups of everything - it still is
interesting. Because no two identical file on both back-ups appear unusable
at the same time - at least so far.

Just wondering - what might be the possible cause/causes - and what might be
done to ensure better transfers. So far we use either a manual 'copy' in
Windows Explorer or sometimes a file-sync utility like SmartSync Pro.

Regards and thanks for any insights.

Mobius
--------
Click to expand...

Hello Mobius:

You have received fine advice from others in this thread. If anything
you back up is mission critical, you may wish to consider making
independent checksums or hashes.

I realize that your data files may not be static so to supplement your
outstanding two backup scheme, please consider:


Take a md5/sha1 checksum before the static file is transfered /and/
after. Immediately you will /independently/ know if the destination
file was written correctly. Reverse the above procedure? Sure!

Caveat: A file's hash can't be checked after it's been compressed. But
it can after it's been uncompressed.

Many checksum utilities are freeware:

<http://www.thefreecountry.com/utilities/free-md5-sum-tools.shtml>

Many web sites, with downloadable elements, will publish the file's hash
in a small separate ASCII text file.

Warm regards,

Pete
 
Mobius said:
We have backed up files and folders routinely innumerable times over the
years for working systems to external drives - mostly USB. These back-ups
have come in might useful a few times!

Sometimes we find that some files on the external drive give a 'corrupt'
or
'crc' or 'damaged' error when tried to be opened. This happens randomly
and
for any file type - exe, doc, html, iso or other.

On a rough average we estimated that about a couple of percent of all such
back up files are thus unusable. While no critical files have been 'lost'
so
far - we always have two separate back-ups of everything - it still is
interesting. Because no two identical file on both back-ups appear
unusable
at the same time - at least so far.

Just wondering - what might be the possible cause/causes - and what might
be
done to ensure better transfers. So far we use either a manual 'copy' in
Windows Explorer or sometimes a file-sync utility like SmartSync Pro.

Regards and thanks for any insights.

Mobius
Click to expand...

So far you've said making copies of files on 2 USB drives. Failures during
read or opening files, not writes. No file is common with problem on either
drive. Am curious as you did not note a commonality, or deny a commonality
between some of your PCs and not others and this problem.
 
Thanks for the helpful pointers. We are considering replacing the external
drives with newer hardware soon - hope that solves the problem!
 

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