Bluestore DB size and onode count

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If anybody has 5 minutes could they just clarify a couple of things for me

1. onode count, should this be equal to the number of objects stored on the OSD?
Through reading several posts, there seems to be a general indication that this is the case, but looking at my OSD's the maths don't
work.

Eg.
ceph osd df
ID CLASS WEIGHT  REWEIGHT SIZE  USE    AVAIL  %USE  VAR  PGS
 0   hdd 2.73679  1.00000 2802G  1347G  1454G 48.09 0.69 115

So 3TB OSD, roughly half full. This is pure RBD workload (no snapshots or anything clever) so let's assume worse case scenario of
4MB objects (Compression is on however, which would only mean more objects for given size)
1347000/4=~336750 expected objects

sudo ceph daemon osd.0 perf dump | grep blue
    "bluefs": {
    "bluestore": {
        "bluestore_allocated": 1437813964800,
        "bluestore_stored": 2326118994003,
        "bluestore_compressed": 445228558486,
        "bluestore_compressed_allocated": 547649159168,
        "bluestore_compressed_original": 1437773843456,
        "bluestore_onodes": 99022,
        "bluestore_onode_hits": 18151499,
        "bluestore_onode_misses": 4539604,
        "bluestore_onode_shard_hits": 10596780,
        "bluestore_onode_shard_misses": 4632238,
        "bluestore_extents": 896365,
        "bluestore_blobs": 861495,

99022 onodes, anyone care to enlighten me?

2. block.db Size
sudo ceph daemon osd.0 perf dump | grep db
        "db_total_bytes": 8587829248,
        "db_used_bytes": 2375024640,

2.3GB=0.17% of data size. This seems a lot lower than the 1% recommendation (10GB for every 1TB) or 4% given in the official docs. I
know that different workloads will have differing overheads and potentially smaller objects. But am I understanding these figures
correctly as they seem dramatically lower?

Regards,
Nick

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