Move to thin LVM as the default configuration

[Eric Harney]

There is not much reason to use thick LVM as the default configuration any longer. Thin LVM performs better w.r.t. snapshots and clones, doesn't need slow volume wiping, and thick LVM offers us no advantages.

We can do this by:
- Allowing "auto" as a setting which will enable Thin LVM on deployments that can turn it on. This enables the default configuration to function regardless of platform, and will assist with upgrades when we decide to change the default.
- Configuring a default max_over_subscription_ratio limit of 1.0 so we have the same behavior as Thick LVM for space management.

[Eric Harney (eharney)]

https://review.openstack.org/#/c/104653

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/104653
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=73746bf94f0433cf96489c3e0c8df226664d395a
Submitter: Jenkins
Branch: master

commit 73746bf94f0433cf96489c3e0c8df226664d395a
Author: Eric Harney <email address hidden>
Date: Mon Jun 16 15:43:51 2014 -0400

    LVM Thin Provisioning auto-detect

    Add the ability to set lvm_type=auto, which will
    enable thin provisioning if the system supports it,
    and the configured volume group either:
    a) has a pool LV with the expected name or
    b) has no LVs

    This, along with thin-provisioning accounting, will
    give a path to move toward thin LVM as the default.

    DocImpact: new value 'auto' for option 'lvm_type'

    Partial-Bug: #1472803

    Change-Id: Idfc1cd749bfd7aec659ab8e80629cc506cd9797a

[Eric Harney (eharney)]

The default is still thick for now.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/266986
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=82dae55232e67f6a593f67f74e642899abc6a2f6
Submitter: Jenkins
Branch: master

commit 82dae55232e67f6a593f67f74e642899abc6a2f6
Author: Eric Harney <email address hidden>
Date: Wed Jan 13 10:29:50 2016 -0500

    Set LVM driver default overprovisioning ratio to 1.0

    This introduces a config option, 'lvm_max_over_subscription_ratio',
    which allows overriding the global max_over_subscription_ratio.

    This is needed because the way we handle configuration with
    multi-backend does not allow setting a value which will be applied
    to each LVM backend without manually setting it in each backend,
    and it would be better to default to a safe overprovisioning
    ratio for the LVM driver. It is often used in smaller deployments
    and POCs which may not have all of the capacity monitoring
    infrastructure used with other drivers, so overprovisioning should
    be an opt-in capability rather than opt-out.

    Partial-Bug: #1472803
    DocImpact: new config option lvm_max_over_subscription_ratio

    Change-Id: I5a214462b573d00d26086512821b4f8cc1db4fc3

[Sean McGinnis (sean-mcginnis)]

Unassigning due to no activity for > 6 months.