On Thu, Oct 18, 2018 at 08:32:56AM -0400, Stephen Gallagher wrote:
On Thu, Oct 18, 2018 at 8:29 AM Matthew Miller
> On Thu, Oct 18, 2018 at 07:58:33AM -0400, Stephen Gallagher wrote:
> > I can't see anyone putting a Server or Atomic Host into hibernation,
> > though. Does this just direct the kernel where that should go if
> > hibernation is requested, or does it reserve space or something for
> > it?
> There might be some use for it for VMs....
Doesn't the hypervisor do that itself for VMs?
You have a choice, but most people do use hypervisor save/restore. It
is rare to see guest S3/S5 save/restore used in VMs.
The hypervisor initiated save/restore VM state to a file will work with
any OS, as it is transparent to the guest. The saved state can also be
explicitly managed by the host mgmt tools, letting you do snapshotting
and rollback of state, if you combine memory state with file snapshots.
The key downside is that it is transparent to the guest, so when you
restore the guest, its clock will be wrong and needs fixing / catching
With guest initiated save/restore you're not using any additional host
resources and its all confined in the guest execution environment. The
guest knows to update its clock upon restore since it is aware of what
is happening. The downside is that not all guest OS are reliable at doing
S3/S5, and for that matter not all hypervisors will actually advertize
S3/S5 support in their BIOS. IIRC, RHEL KVM explicitly disables this.