On 17/01/2022 21.12, Daniel P. Berrangé wrote:
On Mon, Jan 17, 2022 at 08:16:39PM +0100, Thomas Huth wrote:
The list of machine types grows larger and larger each release ... and
it is unlikely that many people still use the very old ones for live
migration. QEMU v1.7 has been released more than 8 years ago, so most
people should have updated their machines to a newer version in those
8 years at least once. Thus let's mark the very old 1.x machine types
as deprecated now.
What criteria did you use for picking v1.7 as the end point ?
I picked everything starting with a "1." this time ;-)
No, honestly, since we don't have a deprecation policy in place yet,
there was no real good criteria around this time. For the machine types
< 1.3 there was a bug with migration, so these machine types could not
be used for reliable migration anymore anyway. But for the newer machine
types, we likely have to decide by other means indeed.
I'm fine with the idea of aging out machine types, but I'd like us
to explain the criteria we use for this, so that we can set clear
expectations for users. I'm not a fan of adhoc decisions that have
different impact every time we randomly decide to apply them.
A simple rule could be time based - eg we could say
"we'll keep machine type versions for 5 years or 15 releases."
one factor is how long our downstream consumers have been keeping
machines around for.
In RHEL-9 for example, the oldest machine is "pc-i440fx-rhel7.6.0"
which IIUC is derived from QEMU 2.12.0. RHEL-9 is likely to rebase
QEMU quite a few times over the coming years, so that 2.12.0 version
sets an example baseline for how long machines might need to live for.
That's 4 years this April, and could potentially be 6-7 years by the
time RHEL-9 stops rebasing QEMU.
Yeah, 5 years still seemed a little bit short to me, that's one of the
reasons why I did not add more machine types in my patch here. I think
with 7 or 8 years, we should be on the safe side.
Any other opinions? And if we agree on an amount of years, where should
we document this? At the top of docs/about/deprecated.rst?