Peter Tribble wrote:
The key advantage of using sparse-root is that there's only one OS to manage.
With whole-root zones, and other heavier solutions, there's an extra OS image
to manage with each virtual system. From an admin perspective, whole-root
zones offer no real advantage over xen/vmware, and while I would (and do)
run sparse-root zones extensively, I would run Xen or VMware rather than
whole-root zones, as they have other capabilities you can leverage.
I think this is incorrect. There is always only a single
OS to manage with zones, sparse or whole-root. There is
always only a single kernel in memory. In terms of the
user-level software management, that has to be done in
both the sparse and whole-root cases. The only difference
is that some new bits don't have to be copied for sparse,
but the pkg metadata must be maintained within the zones
in all cases, along with at least a subset of files.
There are also other admin advantages for zones over VMs.
There is only one kernel sucking up memory. There is massive
scalability on a system with zones vs. VMs. Apps run
at full speed vs. the overhead of a hypervisor and virtual
I/O. You have full observability across all zones using
tools like DTrace. Of course VMs have advantages over zones
too. It depends on what is important to you.
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