Until the resource providers work is done, there is no fix for this.
Under current architecture this is a Won't Fix
** Changed in: nova
Status: New => Won't Fix
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https://bugs.launchpad.net/bugs/1633990
Title:
resize or migrate instance will get failed if two compute hosts are
set in different rbd pool
Status in OpenStack Compute (nova):
Won't Fix
Bug description:
We are now facing a nova operation issue about setting different ceph rbd
pool to each corresponding nova compute node in one available zone. For
instance:
(1) compute-node-1 in az1 and set images_rbd_pool=pool1
(2) compute-node-2 in az1 and set images_rbd_pool=pool2
This setting can normally work fine.
But problem encountered when doing resize/migrate instance. For instance,
when try to resize an instance-1 originally in compute-node-1, then nova will
do schedule procedure, assuming that nova-scheduler get the chosen compute node
is compute-node-2. Then the nova will get the following error:
http://paste.openstack.org/show/585540/.
This exception is because that in compute-node-2 nova can't find pool1 vm1
disk. So is there a way nova can handle this? Similar thing in cinder, you may
see a cinder volume has host attribute like:
host_name@pool_name#ceph.
Why we use such setting is because that while doing storage capacity
expansion we want to avoid the influence of ceph rebalance.
One solution we found is AggregateInstanceExtraSpecsFilter, this can
coordinate working with Host Aggregates metadata and flavor metadata.
We try to create Host Aggregates like:
az1-pool1 with hosts compute-node-1, and metadata {ceph_pool: pool1};
az1-pool2 with hosts compute-node-2, and metadata {ceph_pool: pool2};
and create flavors like:
flavor1-pool1 with metadata {ceph_pool: pool1};
flavor2-pool1 with metadata {ceph_pool: pool1};
flavor1-pool2 with metadata {ceph_pool: pool2};
flavor2-pool2 with metadata {ceph_pool: pool2};
But this may introduce a new issue about the create_instance. Which flavor
should be used? The business/application layer seems need to add it's own
flavor scheduler. And this can also
cause a compute service capacity issue. If choice one flavor to resize, the
scheduler will use the AggregateInstanceExtraSpecsFilter to limit the
destination host to the same rbd pool, what if there is no available compute
host? what if there has no enough memory or CPU? So this is not the best
solution.
So here finally, I want to ask, if there is a best practice about
using multiple ceph rbd pools in one available zone.
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