Description of problem:

Data synced from source to destination is compressed but compression ratio is not as effective as source site.

Build : ceph version 12.2.1-37.el7cp (c16105a12f94b5e65d175d620d8d548055c8d490) luminous (stable)

Steps followed:
*Enabled "zlib" compression on both sites.
*Written 1 bucket with 1 object in source site.Data is compressed.
*Checked the data in destination site. Data is synced and compressed but it was not effective as source site.

Summary:
Primary to Secondary -> original size in Kb :58924
                        Compressed size in local in Kb : 2684,
                        Synced n compressed size in remote in Kb :3802,

Secondary to Primary -> original size in Kb :58924
                        Compressed size in local in Kb : 2684,
                        Synced n compressed size in remote in Kb :3802,


Primary to secondary

Primary site - Written

[root@aircobra ~]# radosgw-admin bucket stats --bucket test1_0 --cluster primary
{
    "bucket": "test1_0",
    "zonegroup": "aa2114c4-e96f-48b0-a023-825239368582",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.116",
    "marker": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.116",
    "index_type": "Normal",
    "owner": "synchronization-user",
    "ver": "0#3",
    "master_ver": "0#0",
    "mtime": "2017-11-03 16:22:40.836903",
    "max_marker": "0#00000000002.2343.5",
    "usage": {
        "rgw.main": {
            "size": 60335136,
            "size_actual": 60338176,
            "size_utilized": 2747804,
            "size_kb": 58922,
            "size_kb_actual": 58924,
            "size_kb_utilized": 2684,
            "num_objects": 1
        }
    },
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}
[root@aircobra ~]# 


Secondary site synced

[root@fortress ~]# radosgw-admin bucket stats --bucket test1_0 --cluster secondary
{
   {
    "bucket": "test1_0",
    "zonegroup": "aa2114c4-e96f-48b0-a023-825239368582",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.116",
    "marker": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.116",
    "index_type": "Normal",
    "owner": "synchronization-user",
    "ver": "0#3",
    "master_ver": "0#0",
    "mtime": "2017-11-03 16:22:40.836903",
    "max_marker": "0#00000000002.2431.1",
    "usage": {
        "rgw.main": {
            "size": 60335136,
            "size_actual": 60338176,
            "size_utilized": 3893016,
            "size_kb": 58922,
            "size_kb_actual": 58924,
            "size_kb_utilized": 3802,
            "num_objects": 1
        }
    },
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}

Secondary to primary
Secondary site - written
[root@fortress ~]# radosgw-admin bucket stats --bucket test2_0 --cluster secondary
{
    "bucket": "test2_0",
    "zonegroup": "aa2114c4-e96f-48b0-a023-825239368582",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.117",
    "marker": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.117",
    "index_type": "Normal",
    "owner": "synchronization-user",
    "ver": "0#3",
    "master_ver": "0#0",
    "mtime": "2017-11-03 16:35:37.268944",
    "max_marker": "0#00000000002.2277.1",
    "usage": {
        "rgw.main": {
            "size": 60335136,
            "size_actual": 60338176,
            "size_utilized": 2747804,
            "size_kb": 58922,
            "size_kb_actual": 58924,
            "size_kb_utilized": 2684,
            "num_objects": 1
        }
    },
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}

Primary site synced
[root@aircobra ~]# radosgw-admin bucket stats --bucket test2_0 --cluster primary
{
    "bucket": "test2_0",
    "zonegroup": "aa2114c4-e96f-48b0-a023-825239368582",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.117",
    "marker": "bf0750fa-3531-4110-a224-2df15c2c445f.204098.117",
    "index_type": "Normal",
    "owner": "synchronization-user",
    "ver": "0#3",
    "master_ver": "0#0",
    "mtime": "2017-11-03 16:35:37.268944",
    "max_marker": "0#00000000002.2203.5",
    "usage": {
        "rgw.main": {
            "size": 60335136,
            "size_actual": 60338176,
            "size_utilized": 3893016,
            "size_kb": 58922,
            "size_kb_actual": 58924,
            "size_kb_utilized": 3802,
            "num_objects": 1
        }
    },
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}
[root@aircobra ~]#