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resize disk down

asked 2014-06-25 13:34:15 -0500

granadol gravatar image

Can Openstack rezise instances down?

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answered 2014-06-25 15:20:20 -0500

mpetason gravatar image

Here's a blueprint discussing this:

The most relevant part:

Resize to a smaller disk can never work if the user already has more data than the new flavor allows - so for consistency any resize to a smaller flavour should be treated as an error.

The question is... will it let you do it via the API -- Maybe, but it should give you an error if it fails. This also may depend on the Hypervisor type and specific configuration options in nova.conf.

More helpful information:

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I have just tried the resize. The hypervisor is KVM. There are errors but nothing that points to a failure. What options should exist in nova.conf to make it happen. No way I have more space because I just resized it up then tried to downsize it.

granadol gravatar imagegranadol ( 2014-06-25 15:25:49 -0500 )edit

So it resizes it down based on the flavor, but then the disk just stays the same. Is this the outcome you are seeing?

libvirt: logs it cannot resize to smaller and just keeps the larger disk
xen: tries to copy contents to a smaller disk, fails if too large
hyperv: always errors out if new disk size is smaller
powervm: silently keeps the larger disk
vmware: (couldn't find where migration code handled resize)

mpetason gravatar imagempetason ( 2014-06-25 15:27:37 -0500 )edit

It does nothing but error with instance not resizing, skipping migration. This happens very quickly and does not register in dashboard.

granadol gravatar imagegranadol ( 2014-06-25 15:32:35 -0500 )edit

Makes sense. You need to edit a few settings in your .conf to allow same host migrations, otherwise it's trying to migrate to other hosts. If you aren't using distributed storage then this fails due to an SSH session opening. Check your error logs for nova on the compute node the instance is on.

mpetason gravatar imagempetason ( 2014-06-25 15:35:58 -0500 )edit

allow_resize_to_same_host = False

Set to True. Restart service. It's trying to migrate the system to another host when you do a resize.

mpetason gravatar imagempetason ( 2014-06-25 15:36:54 -0500 )edit

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Asked: 2014-06-25 13:34:15 -0500

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Last updated: Jun 25 '14