Tks gorka

In this case ,i create a 1GB volume in ceph2. And then use CLI "cinder get-pools --detail" see allocated_capacity_gb as follows:

[root@CG_CEPH ~(keystone_admin)]# cinder get-pools --detail
+-----------------------+----------------------------+
|        Property       |           Value            |
+-----------------------+----------------------------+
| allocated_capacity_gb |             2              |
|     driver_version    |           1.2.0            |
|    filter_function    |            None            |
|    free_capacity_gb   |          18511.51          |
|   goodness_function   |            None            |
|      multiattach      |            True            |
|          name         |      cinder@ceph#ceph      |
|       pool_name       |            ceph            |
|  reserved_percentage  |             0              |
|    storage_protocol   |            ceph            |
|       timestamp       | 2017-07-22T09:52:53.998642 |
|   total_capacity_gb   |          18512.04          |
|      vendor_name      |        Open Source         |
|  volume_backend_name  |            ceph            |
+-----------------------+----------------------------+
+-----------------------+----------------------------+
|        Property       |           Value            |
+-----------------------+----------------------------+
| allocated_capacity_gb |             2              |
|     driver_version    |           1.2.0            |
|    filter_function    |            None            |
|    free_capacity_gb   |          18511.51          |
|   goodness_function   |            None            |
|      multiattach      |            True            |
|          name         |     cinder@ceph2#ceph2     |
|       pool_name       |           ceph2            |
|  reserved_percentage  |             0              |
|    storage_protocol   |            ceph            |
|       timestamp       | 2017-07-22T09:53:31.180495 |
|   total_capacity_gb   |          18512.51          |
|      vendor_name      |        Open Source         |
|  volume_backend_name  |           ceph2            |
+-----------------------+----------------------------+

second step:

After migrating volume to ceph. use CLI "cinder get-pools --detail" see allocated_capacity_gb as follows: 

[root@CG_CEPH ~(keystone_admin)]# cinder get-pools --detail
+-----------------------+----------------------------+
|        Property       |           Value            |
+-----------------------+----------------------------+
| allocated_capacity_gb |             3              |
|     driver_version    |           1.2.0            |
|    filter_function    |            None            |
|    free_capacity_gb   |          18510.02          |
|   goodness_function   |            None            |
|      multiattach      |            True            |
|          name         |      cinder@ceph#ceph      |
|       pool_name       |            ceph            |
|  reserved_percentage  |             0              |
|    storage_protocol   |            ceph            |
|       timestamp       | 2017-07-22T09:57:54.111857 |
|   total_capacity_gb   |          18511.55          |
|      vendor_name      |        Open Source         |
|  volume_backend_name  |            ceph            |
+-----------------------+----------------------------+
+-----------------------+----------------------------+
|        Property       |           Value            |
+-----------------------+----------------------------+
| allocated_capacity_gb |             2              |
|     driver_version    |           1.2.0            |
|    filter_function    |            None            |
|    free_capacity_gb   |          18510.02          |
|   goodness_function   |            None            |
|      multiattach      |            True            |
|          name         |     cinder@ceph2#ceph2     |
|       pool_name       |           ceph2            |
|  reserved_percentage  |             0              |
|    storage_protocol   |            ceph            |
|       timestamp       | 2017-07-22T09:58:31.185126 |
|   total_capacity_gb   |          18511.02          |
|      vendor_name      |        Open Source         |
|  volume_backend_name  |           ceph2            |
+-----------------------+----------------------------+


the allocated_capacity_gb in ceph increased but ceph2 remain the same.This confusing.So it maybe a question。