My system becomes much, much less responsive, every time I clone a VM image. I'm using
virt-manager, and I can see the IO is performed by several
qemu-img convert threads.
I tried to gather some information, and it looked like there might have been a lot of swapping (I/O on the swap partition). I have 8GB RAM, and 2GB swap. During and after the clone,
free -h showed that 100% of the swap space was used. However, that doesn't tell me how much the system was swapping at the time. Something might have filled the swap before I cloned the VM.
I am using a spinning hard drive. My current OS is Fedora Linux 28.
How can I be prepared when this happens, to gather the relevant information, and see whether there is a lot of swapping or not?
I want some sort of record I can look back at, and collate different information. I.e. if I run a simple
iotop command, they will overwrite their old output; I don't want that.