Feature #17350

Updated by Nico C├ęsar 10 months ago

Once #17349 is done, railsapi will have "replicas_desired" with some values that accept several storage classes. As example some are listed in the column "Collection effective value" from the valid entries.

Assumption there are 600 blocks equally distributed in the volumes

h2. Volumes scenario

h3. Scenario 1
<pre>
---
Clusters:
test1:
Collections:
DefaultReplication: 1
Volumes:
test1-nyw5e-000000000000000:
AccessViaHosts:
'http://keep0:25107': {}
test1-nyw5e-111111111111111:
AccessViaHosts:
'http://keep1:25108': {}
</pre>

h3. Scenario 2
<pre>
---
Clusters:
test1:
Collections:
DefaultReplication: 1
Volumes:
test1-nyw5e-000000000000000:
AccessViaHosts:
'http://keep0:25107': {}
test1-nyw5e-111111111111111:
AccessViaHosts:
'http://keep1:25108': {}
StorageClasses:
archival: true
</pre>

h3. Scenario 3
<pre>
---
Clusters:
test1:
Collections:
DefaultReplication: 1
Volumes:
test1-nyw5e-000000000000000:
AccessViaHosts:
'http://keep0:25107': {}
test1-nyw5e-111111111111111:
AccessViaHosts:
'http://keep1:25108': {}
StorageClasses:
archival: true
Read-Only
</pre>

h2. Expected result after tunnign keep balance



|_. Collection Effective Value |_. Volumes scenario | Expected result after keep-balance run |
| {"default": 1} | 1 | 300 blocks in each volume keep0 has 1 copy|
| {"default": 1, "archival": 1} | 1 | impossible, there is no archival class? |
| {"default": 0, "archival": 2} | 1 | impossible, there is no archival class?
|
| {"default": 1} | 2 | 600 blocks in test1-nyw5e-000000000000000 keep0 has 1 copy|
| {"default": 1, "archival": 1} | 2 | keep0 has 1 copy
and 600 blocks in test1-nyw5e-111111111111111 keep1 has 1 copy |
| 3 {"default": 0, "archival": 2} | 600 blocks in test1-nyw5e-000000000000000 and 300 blocks in test1-nyw5e-111111111111111 2 |

To be talked in next grooming session (Feb 16th)

* What are the common usecase ?
* What other scenarios we care about?
* How we address the process of changing configuration and re-running keep-balance?
impossible, there is no 2 archival class keepstores |

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