Hi Brendan
in fact you can alter RocksDB settings by using
bluestore_rocksdb_options config parameter. And hence change
"max_bytes_for_level_base" and others.
Not sure about dynamic level sizing though.
Current defaults are:
"compression=kNoCompression,max_write_buffer_number=4,min_write_buffer_number_to_merge=1,recycle_log_file_num=4,write_buffer_size=268435456,writable_file_max_buffer_size=0,compaction_readahead_size=2097152"
Thanks,
Igor
On 11/13/2018 5:19 AM, Brendan Moloney wrote:
Hi,
I have been reading up on this a bit, and found one particularly
useful mailing list thread [1].
The fact that there is such a large jump when your DB fits into 3
levels (30GB) vs 4 levels (300GB) makes it hard to choose SSDs of an
appropriate size. My workload is all RBD, so objects should be large,
but I am also looking at purchasing rather large HDDs (12TB). It
seems wasteful to spec out 300GB per OSD, but I am worried that I will
barely cross the 30GB threshold when the disks get close to full.
It would be nice if we could either enable "dynamic level sizing"
(done here [2] for monitors, but not bluestore?), or allow changing
the "max_bytes_for_level_base" to something that better suits our use
case. For example, if it were set it to 25% of the default (75MB L0
and L1, 750MB L2, 7.5GB L3, 75GB L4) then I could allocate ~85GB per
OSD and feel confident there wouldn't be any spill over onto the slow
HDDs. I am far from on expert on RocksDB, so I might be overlooking
something important here.
[1]
https://ceph-users.ceph.narkive.com/tGcDsnAB/slow-used-bytes-slowdb-being-used-despite-lots-of-space-free-in-blockdb-on-ssd
[2] https://tracker.ceph.com/issues/24361
Thanks,
Brendan
_______________________________________________
ceph-users mailing list
[email protected]
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
_______________________________________________
ceph-users mailing list
[email protected]
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
