Re: [ovirt-users] VMs seems to be slow, while snapshot delete is happening
On 05/12/2016 03:46 AM, SATHEESARAN wrote:
Hi All,
I have created a VM with 60GB of disk space.
I have started I/O inside the VM, after sometime when the disk was 4GB full,
I took a snapshot of the disk from UI.
I/O kept continuing and the new image file ( overlay file ) was 15GB in
size.
Now I deleted the snapshot.
I think this would initiate block-merges.
During this time, my I/O was were slower, till the snapshot delete is
completed.
Its not very slow, but slow.
Is this a known behavior ?
Hi Satheesaran,
It sounds like this was a live merge, ie snapshot removal while the VM was
running. This is currently implemented as a block commit, where data from
the snapshot (your 15GB overlay, in this case) is merged down.
For snapshot deletion to complete, this means that your concurrent I/O and
the data already in the overlay have to be written into the next-lower
image. So in short, yes, depending on the storage system backing your VM,
I/O may slow down a bit until completion.
HTH,
Greg
Advance thanks,
Satheesaran S
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