# Data Corruption Checking Software



## Osho (May 19, 2010)

Is there software used by Lightroom users to check the large amount of photo data that gets backed up on RAID and/or single external HDDs? I've been trying to identify a dependable solution to the prevention of RAIDing data errors or backing up data errors on non RAID external HDDs as well. Thanks


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## Mark Sirota (May 19, 2010)

Depends on the nature of your backups. Are they just copies of your files, or disk images, or something else?

I have multiple copies of my originals, in identical hierarchies, on multiple disks. I use "diff -rq" (the command line tool, which you can run from Terminal) to compare them every once in a while.


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## Osho (May 19, 2010)

I store or backup first to an internal set of drives, then to a 2TB external standalone HDD, and finally to a RAID1 set of two HDDs. I have backups for Lightroom photos, designs and logos created on a light tablet, typed material and finally the contents of the system drive with it's OS, applications and associated files. 

All of these are in separate folders on a single unpartitioned HDD on the external and RAIDed external HDDs [internally, however, I have four each of 5'' GB drives with the same files allotted proportionately across the four of them]. 

Your solution of typing "diff -rq" in terminal sounds like the right price for sure but can you give me a keystroke how-to? I'm working on my computer skills, but am a little in the weeds at this point. Thanks


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## Mark Sirota (May 19, 2010)

If you're comfortable with command-line tools, it's quite simple.
[list type=decimal]
[li]Open up a Terminal window (it's in Applications/Utilities)[/li]
[li]type "diff -rq _&lt;path1&gt;_ _&lt;path2&gt;_"[/li]
[/list]_&lt;path1&gt;_ and _&lt;path2&gt;_ are the paths to the top of your folder hierarchies. In my case, I'm doing something like 
	
	



```
diff -rq /Volumes/Photos-1/Pictures/Originals /Volumes/Photos-2/Pictures/Originals
```

"Photos-1" and "Photos-2" are the names of two of the disks that hold my originals. If all is well, diff will report nothing. If there are differences, they will be reported.


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## Osho (May 19, 2010)

Thanks, I'll give it a try.


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## Victoria Bampton (May 19, 2010)

Or if you fancy a solution with a UI, Chronosync can do a verified copy and alert you to changes.


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## Osho (May 20, 2010)

I think I will go with a software package just because it makes automatic backups and bootable clones possible not to mention the fact that it will keep me away from aspects of the OS of which I have an imperfect understanding.  But, none of the packages I've examined including Chronosync checks for file and data patency!? Would using Disk Utilities [Mac] and Disk Verify/Repair be adequate? The Terminal command line prompt "diff -rq" sounds like a good alternative but not as "entry level" as Disk Utilities.


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## Victoria Bampton (May 20, 2010)

Chronosync has a 'verified copy data' checkbox in the 'special file/folder handling' section, and if you want to compare ones that are already on disc, setting it up as if it's going to copy and then looking in the Analyze panel will show you a list of all of your files, their sizes and any time differences.

If you're really concerned about image data verification, take a look at ImageVerifier http://basepath.com/ImageIngester/ivinfo.php


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## Osho (May 20, 2010)

When I went to the Chronosync website, I saw the "Analyze" feature but the boilerplate didn't seem to address data corruption specifically and after the amount of looking around I've done, I wasn't optimistic about it's usefulness. But, you've definitely encouraged another look. At this point, along with OWC RAID [to backup the backup], a 2GB La Cie backup"HDD, existing internal "Copy to..." HDDs plus a file and data checker, I think I'm able to recreate a system that'll allow me to sleep better. Thanks for the help. 

BTW, I've been looking at some of voluminous files of past threads and, as a result, have come to really appreciate this forum.


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## Osho (May 20, 2010)

I downloaded the Chronosync/Agent demo, saw the "Verify" checkbox [they should tout this feature more than they do] and will be using the software. The "diff -rq" is also there to investigate.  Thanks for the tip.


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