Hi all,

we run a Ceph Luminous 12.2.12 cluster, 7 osds servers 12x4TB disks each.
Recently we redeployed the osds of one of them using bluestore backend,
however, after this, we're facing Out of memory errors(invoked oom-killer)
and the OS kills one of the ceph-osd process.
The osd is restarted automatically and back online after one minute.
We're running Ubuntu 16.04, kernel 4.15.0-55-generic.
The server has 32GB of RAM and 4GB of swap partition.
All the disks are hdd, no ssd disks.
Bluestore settings are the default ones

"osd_memory_target": "4294967296"
"osd_memory_cache_min": "134217728"
"bluestore_cache_size": "0"
"bluestore_cache_size_hdd": "1073741824"
"bluestore_cache_autotune": "true"

As stated in the documentation, bluestore assigns by default 4GB of
RAM per osd(1GB of RAM for 1TB).
So in this case 48GB of RAM would be needed. Am I right?

Are these the minimun requirements for bluestore?
In case adding more RAM is not an option, can any of
osd_memory_target, osd_memory_cache_min, bluestore_cache_size_hdd
be decrease to fit in our server specs?
Would this have any impact on performance?

Thanks
Jaime

--

Jaime Ibar
High Performance & Research Computing, IS Services
Lloyd Building, Trinity College Dublin, Dublin 2, Ireland.
http://www.tchpc.tcd.ie/ | ja...@tchpc.tcd.ie
Tel: +353-1-896-3725

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