From 3c1994529f5ad1d75240743308bdd156b3984e30 Mon Sep 17 00:00:00 2001 From: Jan Fajerski Date: Mon, 29 Apr 2019 14:52:27 +0200 Subject: [PATCH] doc: update bluestore cache settings and clarify data fraction Fixes: http://tracker.ceph.com/issues/39522 Signed-off-by: Jan Fajerski (cherry picked from commit 9d8336a7f418fe2bb11361dd74a214403b1e5be7) --- .../configuration/bluestore-config-ref.rst | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/doc/rados/configuration/bluestore-config-ref.rst b/doc/rados/configuration/bluestore-config-ref.rst index d7e70ee92c6..507ca5b8c87 100644 --- a/doc/rados/configuration/bluestore-config-ref.rst +++ b/doc/rados/configuration/bluestore-config-ref.rst @@ -231,12 +231,13 @@ The configured cache memory budget can be used in a few different ways: * BlueStore data (i.e., recently read or written object data) Cache memory usage is governed by the following options: -``bluestore_cache_meta_ratio``, ``bluestore_cache_kv_ratio``, and -``bluestore_cache_kv_max``. The fraction of the cache devoted to data -is 1.0 minus the meta and kv ratios. The memory devoted to kv -metadata (the RocksDB cache) is capped by ``bluestore_cache_kv_max`` -since our testing indicates there are diminishing returns beyond a -certain point. +``bluestore_cache_meta_ratio`` and ``bluestore_cache_kv_ratio``. +The fraction of the cache devoted to data +is governed by the effective bluestore cache size (depending on +``bluestore_cache_size[_ssd|_hdd]`` settings and the device class of the primary +device) as well as the meta and kv ratios. +The data fraction can be calculated by +`` * (1 - bluestore_cache_meta_ratio - bluestore_cache_kv_ratio)`` ``bluestore_cache_size`` @@ -264,14 +265,14 @@ certain point. :Description: The ratio of cache devoted to metadata. :Type: Floating point :Required: Yes -:Default: ``.01`` +:Default: ``.4`` ``bluestore_cache_kv_ratio`` :Description: The ratio of cache devoted to key/value data (rocksdb). :Type: Floating point :Required: Yes -:Default: ``.99`` +:Default: ``.4`` ``bluestore_cache_kv_max`` -- 2.47.3