Synchronize Sparse Files – How to Sync VM Disk Images

kvm-virtualizationlinuxrsync

Is there a command, such as rsync, which can synchronise huge, sparse, files from one linux server to another?

It is very important that the destination file remains sparse. It may be longer (but not bigger) than the drive which contains it. Only changed blocks should be sent across the wire.

I have tried rsync, but got no joy. https://groups.google.com/forum/#!topic/mailing.unix.rsync/lPOScZgFE9M

If I write a programme to do this, am I just reinventing the wheel? http://www.finalcog.com/synchronise-block-devices

Thanks,

Chris.

Best Answer

rsync --ignore-existing --sparse ...

To create new files in sparse mode

Followed by

rsync --inplace ...

To update all existing files (including the previously created sparse ones) inplace.

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Linux – How to Copy Large Number of Files Quickly Between Servers

I would recommend tar. When the file trees are already similar, rsync performs very well. However, since rsync will do multiple analysis passes on each file, and then copy the changes, it is much slower than tar for the initial copy. This command will likely do what you want. It will copy the files between the machines, as well as preserve both permissions and user/group ownerships.

tar -c /path/to/dir | ssh remote_server 'tar -xvf - -C /absolute/path/to/remotedir'

As per Mackintosh's comment below this is the command you would use for rsync

rsync -avW -e ssh /path/to/dir/ remote_server:/path/to/remotedir

KVM – How to Increase a KVM Guest’s Disk Space

stop the VM
run qemu-img resize vmdisk.img +10G to increase image size by 10Gb
start the VM, resize the partitions and LVM structure within it normally

Best Answer

Related Solutions

Linux – How to Copy Large Number of Files Quickly Between Servers

KVM – How to Increase a KVM Guest’s Disk Space

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