I can't understand, where my ceph raw space is gone.

```
cluster 90dc9682-8f2c-4c8e-a589-13898965b974
     health HEALTH_WARN 72 pgs backfill; 26 pgs backfill_toofull; 51 pgs backfilling; 141 pgs stuck unclean; 5 requests are blocked > 32 sec; recovery 450170/8427917 objects degraded (5.341%); 5 near full osd(s)
     monmap e17: 3 mons at {enc18=192.168.100.40:6789/0,enc24=192.168.100.43:6789/0,enc26=192.168.100.44:6789/0}, election epoch 734, quorum 0,1,2 enc18,enc24,enc26
     osdmap e3326: 14 osds: 14 up, 14 in
      pgmap v5461448: 1152 pgs, 3 pools, 15252 GB data, 3831 kobjects
            31109 GB used, 7974 GB / 39084 GB avail
            450170/8427917 objects degraded (5.341%)
                  18 active+remapped+backfill_toofull
                1011 active+clean
                  64 active+remapped+wait_backfill
                   8 active+remapped+wait_backfill+backfill_toofull
                  51 active+remapped+backfilling
recovery io 58806 kB/s, 14 objects/s

```

OSD tree (each host has 2 OSD):

```
# id    weight  type name       up/down reweight
-1      36.45   root default
-2      5.44            host enc26
0       2.72                    osd.0   up      1
1       2.72                    osd.1   up      0.8227
-3      3.71            host enc24
2       0.99                    osd.2   up      1
3       2.72                    osd.3   up      1
-4      5.46            host enc22
4       2.73                    osd.4   up      0.8
5       2.73                    osd.5   up      1
-5      5.46            host enc18
6       2.73                    osd.6   up      1
7       2.73                    osd.7   up      1
-6      5.46            host enc20
9       2.73                    osd.9   up      0.8
8       2.73                    osd.8   up      1
-7      0               host enc28
-8      5.46            host archives
12      2.73                    osd.12  up      1
13      2.73                    osd.13  up      1
-9      5.46            host enc27
10      2.73                    osd.10  up      1
11      2.73                    osd.11  up      1

```

Real usage:

```
/dev/rbd0        14T  7.9T  5.5T  59% /mnt/ceph

```

Pool size:

```
osd pool default size = 2

```

Pools:
ceph osd lspools

```
0 data,1 metadata,2 rbd,

```

rados df

```
pool name       category                 KB      objects       clones     degraded      unfound           rd        rd KB           wr        wr KB
data            -                          0            0            0            0           0            0            0            0            0
metadata        -                          0            0            0            0           0            0            0            0            0
rbd             -                15993591918      3923880            0       444545           0        82936      1373339      2711424    849398218
  total used     32631712348      3923880
  total avail     8351008324
  total space    40982720672

```

Raw usage is 4x real usage. As I understand, it must be 2x ?