On 06/08/2014 11:14 PM, Dave Scott wrote:
Hi Wido,
Thanks for your mail!
On 8 Jun 2014, at 19:02, Wido den Hollander <w...@widodh.nl> wrote:
On 06/08/2014 06:23 PM, Dave Scott wrote:
Hi,
Following on from the earlier "[PROPOSAL] Support pure Xen as a hypervisor”,
I’ve added a design doc to the wiki:
https://cwiki.apache.org/confluence/display/CLOUDSTACK/Allow+hosts+running+the+Xen+hypervisor+to+be+managed+via+libvirt
This design would allow people who want to manage their hypervisors purely
through the libvirt tools to choose the Xen hypervisor.
From the code point of view, I want to maximise sharing between the KVM and
Xen code paths, partly to make QA easier and partly to maximise the chance that
adding a feature for “Xen” causes it to work for “KVM” and vice-versa. In
particular this means that, if a genuinely-useful capability is currently
missing from the libvirt libxl driver, I want to implement it rather than work
around it.
Seems like a great route to me! You also want to support Xen+Qemu with this way?
Yes, it should be possible to run fully virtualised VMs with Xen + Qemu. I
think we’ll be able to choose whether to run VMs as PV or HVM.
Ok, but those will be different code paths at some level.
We have to be aware that there might be some storage differences between KVM
and Xen like Ceph which is not fully supported yet by Xen.
Ceph is an interesting one. Xen itself doesn’t know anything about storage—
instead the dom0 takes care of it either via a kernel driver (blkback) or
userspace program (qemu or tapdisk). When I tried to make Ceph work about a
year ago[1] I hit a bug in libxl (the Xen control library). The good news is
the fix made it into Xen 4.4, so with luck we can get it to work.
When Xen runs with Qemu as full HVM it's Qemu which takes care of the
Ceph storage, so in that case it's fixed.
I haven't got a lot of experience with PV Xen. I heard stories of Ceph
being integrated in blktap(2), but never tested it.
If anything is missing in libvirt or the Java bindings we have to fix that
indeed instead of hacking around it.
Great :)
Cheers,
Dave
[1]
http://xenserver.org/discuss-virtualization/virtualization-blog/entry/tech-preview-of-xenserver-libvirt-ceph.html
Wido
Comments appreciated!
Cheers,
Dave
[1]
http://mail-archives.apache.org/mod_mbox/cloudstack-users/201403.mbox/%3ccajgxtbnbmqtq81ralgh2kma7v5wjyzkr3xnyasmkc_br+uk...@mail.gmail.com%3e
