Cannot copy vm image larger than 5gb on Centos 6 running KVM virtualization.

I am running Centos 6.6 64bit as a VM host using KVM. I discovered the issue while trying to copy an image file to a backup location.

If I try to copy a file larger than about 5gb from a mounted 2 tb drive it starts copying but quits at about 5gb and gives different errors depending on how I try to copy the file. The issue is not limited to a single file, it happens to any file larger than 5gb. I believe it may be related to the hard drive itself, I've mounted the hard drive in another system and get the same types of errors.

cp returns this error: input/output error
dmesg shows a bunch of these:

ata3.00: status: { DRDY ERR }
ata3.00: error: { UNC }
ata3.00: configured for UDMA/133
ata3: EH complete
ata3.00: exception Emask 0x0 SAct 0x400 SErr 0x0 action 0x0
ata3.00: irq_stat 0x40000008
ata3.00: failed command: READ FPDMA QUEUED
ata3.00: cmd 60/08:50:9f:70:ef/00:00:03:00:00/40 tag 10 ncq 4096 in
res 41/40:00:a1:70:ef/00:00:03:00:00/40 Emask 0x409 (media error) <F>

I've also tried to clone the vm and it also errors out at about 5gb.

My goal now is to retrieve a copy of this vm image so that I can use it on different hardware. I cannot rebuild the vm from scratch because I do not know all of the configurations that need to be in place. It is a custom spam filter and would require to many hours to reconfigure. What are my options to get a working copy of this vm onto other hardware?

The vm itself runs fine and is is Centos 6.6 64bit also.

Thank you!
Luke HiggsNetwork AdministratorAsked:
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Since the error moves with the disk, when you try it on a different system, everything points to there being a problem with the drive.

Since the disk is semi-working, you might be able to use a program like dd-rescue to get an image of the drive, minus the absolutely unreadable spots.

With the drive image, your VMD file should be present, but may have holes in it. You give the impression that the VM is runnable off of the failing disk, so there's a reasonable chance that the copy-with-possible-holes will be runnable as well. If you're lucky, you can just run normal file system repair and get back a working system.

What if you're not lucky? There exist commercial hard drive recovery companies that make their living off of recovering desparately needed data off of failed or failing hard drives. You can get an estimate from them and compare that with your other choices for rebuilding the spam filter appliance.

Once you get things working, I'm sure you'll immediately set up a regularly scheduled backup for your vital data and VMs.

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Luke HiggsNetwork AdministratorAuthor Commented:
Thank you so much for your help. I'll try dd-rescue to recover the data. I did find a backup of the VM (nearly a year old) on another drive so I can probably rebuild it from that if I need to. Ironically I discovered this problem while putting regular backup schedules for these linux boxes in place - lesson learned!
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