Copy verification tools?

[toke lahti]

Let's say I copy one terabyte quite full gpt/jhfs+ disk to another in osx with CCC.
What would be the most efficient way to verify there's no data degradation?
GUI needed.

I also have some old system disk images compressed with 7zx, but they won't open.
So there has been some data degradation at some point when copying them from disk to disk.
Any reasonable way to see inside of them at all?

 

[BrianBaughn]

You can read more at the Bombich website but CCC verifies the clone. What happens after that depends on the disk and so forth. CCC cannot guarantee any copy beyond the instant it is created.

For the old images I would try Zipeg, The Unarchiver or whatever else you can find.

 

[toke lahti]

Great idea!
I didn't thought this a year ago, when I tried to find how to do this with CCC.
CCC verifies the copy before copying, so I thought it doesn't help, since I'm copying to empty disk.
Also their product is so heavily focused on making backup clones of system disk, that their knowledge base says that verifying is done by booting a mac from a clone and seeing if it works.

What I will do in the future is, that I copy the stuff to empty drive with CCC and after that I copy everything again. The second time copying will verify that the already copied files are identical than the files on the source side, when "find and replace corrupt files" option is checked.

 

[Weaselboy]

that their knowledge base says that verifying is done by booting a mac from a clone and seeing if it works.

Just to clarify a bit (you may already realize this) that verify process just verifies the cloned disk will boot. It does not verify all the files got copied over properly.

To verify everything was copied over properly you need to enable the checksum option discussed in the CCC documentation here. What that does is copies a file over then compares the MD5 checksum of the copied file to that of the original to make sure they match and you got an accurate copy. This option is disabled by default. Just be warned, if you turn that option on, your CCC clones will take a looooonnng time.

 

[toke lahti]

I have no problem keeping disks spinning 15 hours a day.
And that "Find and replace corrupted files" has been checked.

But seems to be that I still will use kdiff3.app for verifying. If there's a hitch, you can see where it is...

 

[ocabj]

https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man1/md5.1.html