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