Is it impossible to copy large files exactly? Checksums not consistent.

[DnaielPartstone]

I made a disk image of my Steam PC which comes out to about 676GB. I write the image to a second hard drive and have the software (Acronis True Image) also perform a verfication. Then I produce a checksum. Next I copy that image to an external hard drive. I also produce a checksum of that copy. But the checksums never match. I've done this whole process four times now, and that takes a really long time. So, does Windows have trouble copying very large files to external drives exactly? I really don't know how to back up this image.

[_I_]

if windows is running, and you are copying it, the page file and windows registry files are always being modified, and will never be the same for more than a few seconds

arconis does a very good job, just use the backup

[DnaielPartstone]

Oh, I use the USB drive to boot from Acronis and make the images from that, so Windows isn't running at all. But what you're saying shouldn't matter anyway because once the image is made, it's that image I'm copying. Windows shouldn't do anyting to modify it while I'm copying it.

[Azza ☠]

Data is binary 1s and 0s, it's not impossible to get 100% valid, but it depends how you are transfering it...

Large files over wireless or internet can drop packets of data, this is attempted to be resent and confirmed, but not 100% all the time.

Copying from hard drive to hard drive with extremely large files will depend on memory/cache and also the hard drive quality itself. In some cases, the hard drive heats up from prolonged (hours and hours) worth of copying, it will actually cause errors... as it never has a chance to rest.

It would be a good idea if possible: Check/Scan disk the hard drive you are about to copy first to ensure it doesn't already have any issues. Then full format or clean the target destination. This will help prevent bad sectors, etc.

You could also use a tool to split the file into chucks, with CRC protection (verifying they are valid).

Consider using a third party copy tool, which has check/recover, such as TeraCopy:
http://www.codesector.com/teracopy

[76561198258988800]

Check your RAM for errors using MemTest86+ as the data is stored in memory each time before being committed to disk.

I see this a lot on older PCs and PCs that never got burned in.

99% of the time the cause is defective RAM.

[Bad 💀 Motha]

And also anytime u make an ISO/Image backup (or even a CD/DVD Burn)
Use software that allows the "Verify/Validate" type of option; so after the backup says completed/success it can then re-check the newly created image for any inconsistency. Thus helping ensure you have a "working" image and not a false sense of backup that "might" fail when u go to revert back using that.

[Korupt]

the only way to get the checksums to match is to boot to a loader disk and run the backup software then, the checksum will be the same because both hhd will not have been accessed
acronis have abootloader software to do backups that is perfect,
we use it to mopve physical pc's to cloud/ virtual all the time

[Seven7]

What OS installed? What Acronis version?

I noticed that many of the program to create images of disks and partitions do not work correctly with the system partition, for example, restore points are lost - I think it's because they are encrypted with BitLocker? Yet it probably depends on the version of the operating system and version of image creation program - free version that can be downloaded from hard disk manufacturers is very outdated, and have problems with W7, not to mention the W8, 10.

[DnaielPartstone]

I ran a checksum of the disk image on the internal hd and the checksum is still the same, so that image appears to be fine.

I did a full format before copying, though I didn't check for errors. I also haven't yet checked the ram. I'll start on those probably tonight. But both hd and ram are fairly new and lightly used, so I don't expect any issues there. But you never know.

At this point, I'm about 95% certain it's the ext hd. I use a WD My Book, and these are often touch-and-go. They're notorious for power connection issues. I guess the best thing I can do right now is get another int hd and then work from that one.

Originally posted by Bad-Motha:

And also anytime u make an ISO/Image backup (or even a CD/DVD Burn)
Use software that allows the "Verify/Validate" type of option; so after the backup says completed/success it can then re-check the newly created image for any inconsistency. Thus helping ensure you have a "working" image and not a false sense of backup that "might" fail when u go to revert back using that.

From my original post:
"I write the image to a second hard drive and have the software (Acronis True Image) also perform a verfication."

Originally posted by Seven7:

What OS installed? What Acronis version?

Win7, True Image home 2014
8G of ram.

I noticed that many of the program to create images of disks and partitions do not work correctly with the system partition

Still, the checksum of the image that was created to the second hd should have the same checksum after it's copied to the ext hd.

Originally posted by Azza ☠:

Data is binary 1s and 0s, it's not impossible to get 100% valid, but it depends how you are transfering it...

Via USB 3.0 cable to ext hd.

It would be a good idea if possible: Check/Scan disk the hard drive you are about to copy first to ensure it doesn't already have any issues. Then full format or clean the target destination. This will help prevent bad sectors, etc.

Yeah, that's a good idea. I'll make that a regular part of backups from now on, even with new drives.

You could also use a tool to split the file into chucks, with CRC protection (verifying they are valid).

I might do this, too. At least I could do checksums much faster and narrow down any bad volumes.

Thanks, everyone.