Description of problem:

The partition power of the deployed Swift rings both on the undercloud and overcloud are set to 18, which is way too high. It will create serious problems later on small deployments, especially with replication.

Using a partition power of 18 creates 262.144 partitions in the cluster. If these are spread only across 3 disks (for example only the controller nodes), each partition will be replicated individually - and this takes a lot of time. Additionally, a lot of extra inodes will be created, and depending on the usage one might suffer from a inode cache misses, slowing down the whole node.

Version-Release number of selected component (if applicable):

All OSP releases that use TripleO.

How reproducible:

Always

Steps to Reproduce:
1. Deploy using OOO/director.
2. Check partition power on under- and overcloud using "swift-ring-builder /etc/swift/object.builder"

Actual results:
Partition power of 18. This is the default in puppet-swift if nothing else is defined.

Expected results:
Way lower partition power, for example 10 for small deployments with only a few disks.

Additional info:
Please note that it is not possible to lower the partition power once the cluster has been deployed. Increasing the partition power later on is proposed as a patch upstream, but not yet merged; therefore starting with a lower value is much safer than using a high value that will create trouble later.

There is already a partition power of 10 defined in tripleo-heat-templates, but this is not used. Looking at /etc/puppet/hieradata/puppet-stack-config.yaml on the undercloud I see this:

tripleo::ringbuilder::part_power: 10
tripleo::ringbuilder::replicas: 3
tripleo::ringbuilder::min_part_hours: 1
swift_mount_check: false
swift::ringbuilder::replicas: 1

I think the first line should be "swift::ringbuilder::part_power: 10"? Also, replicas is defined twice, and the one with "3" is unused (which makes sense, because there is only a single disk on the undercloud).

On the overcloud I see this in /etc/puppet/hieradata/service_configs.yaml:

swift::ringbuilder::part_power: 10
tripleo::profile::base::swift::ringbuilder::replicas: 3

I think this should be "tripleo::profile::base::swift::ringbuilder::part_power: 10?

Using a partition power of 10 creates 2^10 = 1024 partitions. Each partition is replicated 3 times, therefore a total of 3072 partitions will be spread across all disks. It is recommended to use at least ~ 100 partitions per disk; 3072 partitions is enough for up to ~ 30 disks (even more disks is usable, but data gets less evenly distributed then). Bigger deployments should use a higher value depending on the number of disks on initial deployment as well as expected growth.