OT And I thought I was being so smart...

TeetimeNC wrote on 12/16/2014, 12:21 PM
Some time ago I decided to it would be smart to set up a mirror of my archive disk rather than include it in my regular backups. It wasn't :-(. When the archive disk became corrupt synctoy dutifully duplicated the corruption onto the mirrored disk. At least I think that is what happened. Bottom line - both the archive disk and its mirror are corrupt.

In an attempt to recover at least some of the archived Vegas projects I purchased Wondershare but I'm not having much luck with it. I can "recover" some VEG's, MTS's, JPG's, etc. but when I attempt to open them their respective application reports them as corrupt. For a few of the corrupt files I have a good copy stored elsewhere. When I compare the corrupt to the good copy they both have the same number of bytes and date, but when I open them in a hex editor the internals are different.

I am at a loss as to what caused the corruption. The three other HD's in that PC are ok so I doubt it was any type of malware. At this point I'm not very hopeful of recovering these archives, but am posting this just in case there is something I'm not considering here.

More importantly, how do I guard against this going forward? My archive workflow is that I accumulate archived projects on a removable HD. When it is filled I remove it and replace it with a new HD. I suppose I could set up a differential backup of the archive HD, and then blow it away when its archive HD is removed. Question: would a differential backup detect a file change even though the date and size of the file has remained the same (as happened with my corrupted files)? What would you do to guard against data loss while the archive HD is in the system?

/jerry

Comments

johnmeyer wrote on 12/16/2014, 1:06 PM
Various answers:

1. More than one backup. One backup is generally not enough. One daily, one weekly, one off-site. There are lots of strategies, but most involve at least three backups.

2. Incremental or differential backup. Both strategies keep the original backup intact, and only backup those files that have changed since the last full backup (incremental); or since the last partial backup (differential). The latter makes the best use of space, but you have to use ALL the differential backups since the last full backup. Either one will reduce the likelihood of propagating errors from your main disk drive.

3. Run CHKDSK or Scandisk before running your backup. If the corruption is at the disk level, this will highlight those problems.

4. Verify your existing backup against your main drive. I think you can find software that can do a CRC compare between the backup and your main drive, and give you a list of files that are truly different. If you start finding files that are flagged as changed, but which you know haven't been touched (by you), then you can suspect corruption and go looking for problems before you do a backup.

riredale wrote on 12/16/2014, 3:53 PM
John, not wishing to be nitpicky, but your differential and incremental definitions are accidentally reversed.
johnmeyer wrote on 12/16/2014, 7:51 PM
John, not wishing to be nitpicky, but your differential and incremental definitions are accidentally reversed. Busted.

I did it from memory, and I never could remember which term refers to which strategy. I'll leave my post alone so your comment will continue to make sense.
farss wrote on 12/16/2014, 8:07 PM
The best tool I've found for making backup copies is Beyond Compare.
At least with that whilst it involves me doing some work I have complete control.

Bob.
MikeyDH wrote on 12/16/2014, 9:04 PM
Bob, looks interesting. How much work would be required and where do you keep the back up?
Laurence wrote on 12/16/2014, 11:04 PM
Wow, I would have thought that the redundant disk would have been safe from errors as well.
farss wrote on 12/17/2014, 12:36 AM
[I]" How much work would be required and where do you keep the back up? "[/I]

Not much work, for my video PC I have one folder per job and I pretty much copy camera files onto a USB drive once they're all captured and then use Beyond to check that I've got everything as I work.

For my software development I copy files to the NAS and back that up using Beyond to a USB drive.

Beyond Compare can be use rules for the comparison which is very handy.
e.g. the Thumbs.db file that Windows generates for folders that contain images, it could be setup to ignore .sfk files and/or .bak files


Bob.