Dear Igor, thanks, done: https://tracker.ceph.com/issues/44878 .
================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Igor Fedotov <ifedo...@suse.de> Sent: 01 April 2020 12:14:02 To: Frank Schilder; ceph-users Subject: Re: [ceph-users] Bluestore compression parameters in ceph.conf not used in mimic 13.2.8? Hi Frank, answering the second part. The following settings look senseless indeed: bluestore_compression_min_blob_size_ssd 8192 bluestore_min_alloc_size_ssd 16384 Presumably this was an incomplete backport from Nautilus which has proper numbers: 32K and 16K respectively. Fell free to create a ticket. Thanks, Igor On 4/1/2020 12:44 PM, Frank Schilder wrote: > Dear all, > > I have two observations regarding bluestore compression config: > > 1) ceph.conf settings seem to be ignored. > 2) The SSD default values seem not to save space using compression. > > > To 1) We are running a mimic 13.2.8 cluster with OSDs deployed under mimic > 13.2.2. Back then the interpretation of compression parameters was messed up, > which has been fixed along the way from 13.2.2 to 13.2.8. To get it to work > properly under 13.2.2 I needed to include these settings in ceph.conf: > > [osd] > bluestore compression mode = aggressive > bluestore compression min blob size hdd = 262144 > > and then also enable compression on all pools that should use compression. > These settings are still present in ceph.conf, but they seem to be ignored > when populating the config data base on mon startup or querying config > parameters: > > # ceph config get osd.16 bluestore_compression_min_blob_size_hdd > 131072 > > However: > > # ceph tell osd.16 config get bluestore_compression_min_blob_size_hdd > 262144 > > and: > > # ceph config show osd.16 > NAME VALUE SOURCE > OVERRIDES IGNORES > bluestore_compression_min_blob_size_hdd 262144 file > > This is really confusing. Is this intended? Which values will be used when > deploying new OSDs? > > In general, it would really be helpful if one could query daemon/parameter > groups as in " ceph config get osd bluestore_compression_min_blob_size_hdd" > to get a list right away. > > > To 2) In a long-long-ago discussion about how compression works, I was told > that a blob of bluestore_compression_min_blob_size will be compressed and > then distributed over a number of allocations of bluestore_min_alloc_size. > The defaults for HDD and SSD are: > > bluestore_compression_min_blob_size_hdd 131072 > bluestore_min_alloc_size_hdd 65536 > > bluestore_compression_min_blob_size_ssd 8192 > bluestore_min_alloc_size_ssd 16384 > > If this explanation of the compression method is correct, these defaults > allow up to 50% savings for HDD, but, erm, 0% for SSD as the uncompressed > blob will use the same amount of space as the compressed one as both will > require the same allocation size. > > Did something change here? Are compressed blobs now co-located in allocations? > > > Thanks for your help, > ================= > Frank Schilder > AIT Risø Campus > Bygning 109, rum S14 > _______________________________________________ > ceph-users mailing list -- ceph-users@ceph.io > To unsubscribe send an email to ceph-users-le...@ceph.io _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io
