> -----Original Message-----
> From: ceph-users [mailto:[email protected]] On Behalf Of Mark
> Nelson
> Sent: 10 September 2018 18:27
> To: [email protected]
> Subject: Re: [ceph-users] Bluestore DB size and onode count
>
> On 09/10/2018 12:22 PM, Igor Fedotov wrote:
>
> > Hi Nick.
> >
> >
> > On 9/10/2018 1:30 PM, Nick Fisk wrote:
> >> 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.
> > onode_count is the number of onodes in the cache, not the total number
> > of onodes at an OSD.
> > Hence the difference...
Ok, thanks, that makes sense. I assume there isn't actually a counter which
gives you the total number of objects on an OSD then?
> >>
> >> 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?
> > Just in case - is slow_used_bytes equal to 0? Some DB data might
> > reside at slow device if spill over has happened. Which doesn't
> > require full DB volume to happen - that's by RocksDB's design.
> >
> > And recommended numbers are a bit... speculative. So it's quite
> > possible that you numbers are absolutely adequate.
>
> FWIW, these are the numbers I came up with after examining the SST files
> generated under different workloads:
>
> https://protect-eu.mimecast.com/s/7e0iCJq9Bh6pZCzILpy?domain=drive.google.com
>
Thanks for your input Mark and Igor. Mark I can see your RBD figures aren't too
far off mine, so all looks to be as expected then.
> >>
> >> Regards,
> >> Nick
> >>
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> >
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