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new layout doc: add examples of unexpected layout, to explain

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Alex Auvolat 2023-09-22 09:49:07 +02:00
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doc/book/operations/layout.md
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@ -75,3 +75,111 @@ If you are using the `garage` CLI to script layout changes, follow the following
- **Only call `garage layout apply` once**, and call it **strictly after** all - **Only call `garage layout apply` once**, and call it **strictly after** all
of the `layout assign` and `layout remove` commands have returned. of the `layout assign` and `layout remove` commands have returned.
## Understanding unexpected layout calculations
### Example 1
```
$ garage layout show
==== CURRENT CLUSTER LAYOUT ====
ID Tags Zone Capacity Usable capacity
b10c110e4e854e5a node1 dc1 1000.0 MB 1000.0 MB (100.0%)
a235ac7695e0c54d node2 dc2 1000.0 MB 1000.0 MB (100.0%)
62b218d848e86a64 node3 dc3 1000.0 MB 1000.0 MB (100.0%)
Zone redundancy: maximum
Current cluster layout version: 6
==== STAGED ROLE CHANGES ====
ID Tags Zone Capacity
a11c7cf18af29737 node4 dc1 1000.0 MB
==== NEW CLUSTER LAYOUT AFTER APPLYING CHANGES ====
ID Tags Zone Capacity Usable capacity
b10c110e4e854e5a node1 dc1 1000.0 MB 1000.0 MB (100.0%)
a11c7cf18af29737 node4 dc1 1000.0 MB 0 B (0.0%)
a235ac7695e0c54d node2 dc2 1000.0 MB 1000.0 MB (100.0%)
62b218d848e86a64 node3 dc3 1000.0 MB 1000.0 MB (100.0%)
Zone redundancy: maximum
==== COMPUTATION OF A NEW PARTITION ASSIGNATION ====
Partitions are replicated 3 times on at least 3 distinct zones.
Optimal partition size: 3.9 MB (3.9 MB in previous layout)
Usable capacity / total cluster capacity: 3.0 GB / 4.0 GB (75.0 %)
Effective capacity (replication factor 3): 1000.0 MB
A total of 0 new copies of partitions need to be transferred.
dc1 Tags Partitions Capacity Usable capacity
b10c110e4e854e5a node1 256 (0 new) 1000.0 MB 1000.0 MB (100.0%)
a11c7cf18af29737 node4 0 (0 new) 1000.0 MB 0 B (0.0%)
TOTAL 256 (256 unique) 2.0 GB 1000.0 MB (50.0%)
dc2 Tags Partitions Capacity Usable capacity
a235ac7695e0c54d node2 256 (0 new) 1000.0 MB 1000.0 MB (100.0%)
TOTAL 256 (256 unique) 1000.0 MB 1000.0 MB (100.0%)
dc3 Tags Partitions Capacity Usable capacity
62b218d848e86a64 node3 256 (0 new) 1000.0 MB 1000.0 MB (100.0%)
TOTAL 256 (256 unique) 1000.0 MB 1000.0 MB (100.0%)
```
### Example 2
```
==== CURRENT CLUSTER LAYOUT ====
ID Tags Zone Capacity Usable capacity
b10c110e4e854e5a node1 dc1 1000.0 MB 500.0 MB (50.0%)
a11c7cf18af29737 node4 dc1 1000.0 MB 500.0 MB (50.0%)
a235ac7695e0c54d node2 dc2 1000.0 MB 1000.0 MB (100.0%)
62b218d848e86a64 node3 dc3 1000.0 MB 1000.0 MB (100.0%)
Zone redundancy: maximum
Current cluster layout version: 8
==== STAGED ROLE CHANGES ====
ID Tags Zone Capacity
a11c7cf18af29737 node4 dc3 1000.0 MB
==== NEW CLUSTER LAYOUT AFTER APPLYING CHANGES ====
ID Tags Zone Capacity Usable capacity
b10c110e4e854e5a node1 dc1 1000.0 MB 1000.0 MB (100.0%)
a235ac7695e0c54d node2 dc2 1000.0 MB 1000.0 MB (100.0%)
62b218d848e86a64 node3 dc3 1000.0 MB 753.9 MB (75.4%)
a11c7cf18af29737 node4 dc3 1000.0 MB 246.1 MB (24.6%)
Zone redundancy: maximum
==== COMPUTATION OF A NEW PARTITION ASSIGNATION ====
Partitions are replicated 3 times on at least 3 distinct zones.
Optimal partition size: 3.9 MB (3.9 MB in previous layout)
Usable capacity / total cluster capacity: 3.0 GB / 4.0 GB (75.0 %)
Effective capacity (replication factor 3): 1000.0 MB
A total of 128 new copies of partitions need to be transferred.
dc1 Tags Partitions Capacity Usable capacity
b10c110e4e854e5a node1 256 (128 new) 1000.0 MB 1000.0 MB (100.0%)
TOTAL 256 (256 unique) 1000.0 MB 1000.0 MB (100.0%)
dc2 Tags Partitions Capacity Usable capacity
a235ac7695e0c54d node2 256 (0 new) 1000.0 MB 1000.0 MB (100.0%)
TOTAL 256 (256 unique) 1000.0 MB 1000.0 MB (100.0%)
dc3 Tags Partitions Capacity Usable capacity
62b218d848e86a64 node3 193 (0 new) 1000.0 MB 753.9 MB (75.4%)
a11c7cf18af29737 node4 63 (0 new) 1000.0 MB 246.1 MB (24.6%)
TOTAL 256 (256 unique) 2.0 GB 1000.0 MB (50.0%)
```