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Luke Higgs

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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!
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Luke Higgs


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!