difference between instances vs virtual machines in used_now

asked 2019-09-19 23:20:35 -0500

br gravatar image
summary of resource usage of all of the instances running on the host:

$ openstack host show devstack
+----------+----------------------------------+-----+-----------+---------+
| Host     | Project                          | CPU | MEMORY MB | DISK GB | 
+----------+----------------------------------+-----+-----------+---------+
| devstack | (total)                          | 2   | 4003      | 157     |
| devstack | (used_now)                       | 3   | 5120      | 40      |
| devstack | (used_max)                       | 3   | 4608      | 40      |
| devstack | b70d90d65e464582b6b2161cf3603ced | 1   | 512       | 0       |
| devstack | 66265572db174a7aa66eba661f58eb9e | 2   | 4096      | 40      |
+----------+----------------------------------+-----+-----------+---------+

The CPU column shows the sum of the virtual CPUs for instances running on the host.

The MEMORY MB column shows the sum of the memory (in MB) allocated to the instances that run on the host.

The DISK GB column shows the sum of the root and ephemeral disk sizes (in GB) of the instances that run on the host.

The row that has the value used_now in the PROJECT column shows the sum of the resources allocated to the instances that run on the host, plus the resources allocated to the virtual machine of the host itself.

The row that has the value used_max in the PROJECT column shows the sum of the resources allocated to the instances that run on the host.

Question:

What is the difference between instances and virtual machine in the used_now explanation?

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Comments

This is very strange and looks like a documentation bug to me.

Bernd Bausch gravatar imageBernd Bausch ( 2019-09-20 00:27:53 -0500 )edit

I am also feeling the same... but when I googled even in redhat website also same thing documented.... https://access.redhat.com/documentati... So I thought let me check with experts in the forum....

br gravatar imagebr ( 2019-09-20 01:10:35 -0500 )edit

I suggest you ask this on the distribution list. Put [nova] (with the square brackets) in the subject.

Bernd Bausch gravatar imageBernd Bausch ( 2019-09-20 01:19:08 -0500 )edit

There is no such thing as "virtual machine" in OpenStack. Instances are created using VMs, or containers, or baremetal. In other words, a VM can be a means of implementation, but strictly speaking it's not an OpenStack object.

Bernd Bausch gravatar imageBernd Bausch ( 2019-09-20 01:19:52 -0500 )edit