On Wed, 2020-12-23 at 22:29 +0800, Qiyu Yan wrote: > Patrick O'Callaghan <pocallaghan@xxxxxxxxx> 于2020年12月23日周三 下午9:29写道： > > > > I have a directory I use to hold a Windows VM disk image > > (/home/Windows/...), and would like to snapshot it before playing with > > the QEMU settings. However it's already part of the /home subvolume, so > > is there a way of splitting it off on its own without having to create > > a new subvolume and sending the contents over? AFAIK subvolumes can be > > hierarchical so it would seem like a useful thing to be able to convert > > a subtree without all the copying, but the man page doesn't seem to > > address it. > > You could create a subvolume, use cp --reflink=always to create a > reflink, and delete the old directory, this turns a directory into > subvolume easily without actual copying. But I don't suggest you do > so, since using snapshot/reflink on VM images will make it > Copy-on-Write, VM images should be nocow for performance. > > But can anyone figure out if creating a reflink then removing old > references before any write to the file happens turns on CoW for the > file? I am not sure. But writing after snapshot definitely turns on > CoW. So, if I understand correctly, I can't in fact snapshot a VM without incurring a COW penalty, independently of how I do it? poc _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx
