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[Bug 1870357] [NEW] raw disk usage is not correctly reported during resource update

 

Public bug reported:

Description
===========

available_disk_least r(free disk for a new instance) seems not be calculated
correctly when instance is in raw (images_type=raw) and preallocate_space option is not set.
This may lead  placement/scheduler to take wrong decision regarding space availabilty on hosts.

when total amount of over_committed_disk_size is evaluated on a host, it seems that in 
raw disk type case it is always set to 0.


Steps to reproduce

===========
on a master devstack:

. devstack/openrc admin admin
$openstack hypervisor show alex-devstack | grep  available_least
| disk_available_least | 381

# create an instance with 80GB of disk with qcow2 by default:
$openstack server create  --flavor m1.large --image cirros-0.4.0-x86_64-disk --nic net-id=private  alex

# few seconds later we can see disk available is minus by 80, all is fine.
$ openstack hypervisor show alex-devstack | grep  available_least
| disk_available_least | 301     

# delete instance
$ openstack server delete xxx

# Now set images_type = raw in [libvirt] section in /etc/nova/nova-cpu.conf
$ grep images_type /etc/nova/nova-cpu.conf 
images_type = raw
# restart compute
$ sudo service devstack@n-cpu restart

# respawn the same instance, it will create a instance with raw disk now
$openstack server create  --flavor m1.large --image cirros-0.4.0-x86_64-disk --nic net-id=private  alex

# few seconds later we can see disk available is minus by only by 3GB which is not correct:
openstack hypervisor show alex-devstack | grep  available_least
| disk_available_least | 378

# only allocated size use is decreased:
$ ls -lhs /opt/stack/data/nova/instances/31e46f53-6223-40c3-ad84-0f19d10b52be/disk
2.6G -rw-r--r-- 1 libvirt-qemu kvm 80G Apr  1 10:00 /opt/stack/data/nova/instances/31e46f53-6223-40c3-ad84-0f19d10b52be/disk

Expected result
===============
calculation of over_committed_disk_size must be done for raw disk (at least on not preallocated one)

Actual result
=============
over_committed_disk_size is set to 0 in all cases for raw disk.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1870357

Title:
  raw disk usage is not correctly reported  during resource update

Status in OpenStack Compute (nova):
  New

Bug description:
  Description
  ===========

  available_disk_least r(free disk for a new instance) seems not be calculated
  correctly when instance is in raw (images_type=raw) and preallocate_space option is not set.
  This may lead  placement/scheduler to take wrong decision regarding space availabilty on hosts.

  when total amount of over_committed_disk_size is evaluated on a host, it seems that in 
  raw disk type case it is always set to 0.

  
  Steps to reproduce

  ===========
  on a master devstack:

  . devstack/openrc admin admin
  $openstack hypervisor show alex-devstack | grep  available_least
  | disk_available_least | 381

  # create an instance with 80GB of disk with qcow2 by default:
  $openstack server create  --flavor m1.large --image cirros-0.4.0-x86_64-disk --nic net-id=private  alex

  # few seconds later we can see disk available is minus by 80, all is fine.
  $ openstack hypervisor show alex-devstack | grep  available_least
  | disk_available_least | 301     

  # delete instance
  $ openstack server delete xxx

  # Now set images_type = raw in [libvirt] section in /etc/nova/nova-cpu.conf
  $ grep images_type /etc/nova/nova-cpu.conf 
  images_type = raw
  # restart compute
  $ sudo service devstack@n-cpu restart

  # respawn the same instance, it will create a instance with raw disk now
  $openstack server create  --flavor m1.large --image cirros-0.4.0-x86_64-disk --nic net-id=private  alex

  # few seconds later we can see disk available is minus by only by 3GB which is not correct:
  openstack hypervisor show alex-devstack | grep  available_least
  | disk_available_least | 378

  # only allocated size use is decreased:
  $ ls -lhs /opt/stack/data/nova/instances/31e46f53-6223-40c3-ad84-0f19d10b52be/disk
  2.6G -rw-r--r-- 1 libvirt-qemu kvm 80G Apr  1 10:00 /opt/stack/data/nova/instances/31e46f53-6223-40c3-ad84-0f19d10b52be/disk

  Expected result
  ===============
  calculation of over_committed_disk_size must be done for raw disk (at least on not preallocated one)

  Actual result
  =============
  over_committed_disk_size is set to 0 in all cases for raw disk.

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