ceph cache pool配置
https://my.oschina.net/hanhanztj/blog/515410
0.引入
本文介绍如何配置cache pool tiering. cache pool的作用是提供可扩展的cache，用来缓存ceph的热点数据或者直接用来作为高速pool。如何建立一个cache pool:首先利用ssd盘做一个虚拟的bucket tree，
然后创建一个cache pool,设置其crush映射rule和相关配置，最后关联需要用到的pool到cache pool。
1.建立ssd bucket tree
这是新增ssd bucket(vrack)后的osd tree。其中osd.1 osd.0 osd.2使用的是ssd盘。如何创建将简单，无非是调整或新增osd到bucket tree下。
# ceph osd tree
ID WEIGHT TYPE NAME UP/DOWN REWEIGHT PRIMARY-AFFINITY
-1 6.00000 root default
-2 6.00000 room test
-3 3.00000 rack r1
-7 1.00000 host H09
3 1.00000 osd.3 up 1.00000 1.00000
-9 1.00000 host H07
5 1.00000 osd.5 up 1.00000 1.00000
-10 1.00000 host H06
6 1.00000 osd.6 up 1.00000 1.00000
-4 3.00000 rack vrack
-6 1.00000 host vh06
1 1.00000 osd.1 up 1.00000 1.00000
-8 1.00000 host vh07
2 1.00000 osd.2 up 1.00000 1.00000
-5 1.00000 host vh09
0 1.00000 osd.0 up 1.00000 1.000002.修改crushmap
#ceph osd getcrushmap -o map
#crushtool -d map -o map.txt
#vi map.txt 添加replicated_ruleset_cache crush策略，从vrack机架选择osd
rule replicated_ruleset {
ruleset 0
type replicated
min_size 1
max_size 10
step take r1
step chooseleaf firstn 0 type host
step emit
}
rule replicated_ruleset_cache {
ruleset 1
type replicated
min_size 1
max_size 10
step take vrack
step chooseleaf firstn 0 type host
step emit
}
#crushtool -c map.txt -o map.new
#ceph osd setcrushmap -i map.new
3. 创建cache pool
指定新建的pool的crush rules 为replicated_ruleset_cache
#ceph osd pool create rbd.cache 128 128
#ceph osd pool set rbd.cache crush_ruleset 1
4. 为rbd pool添加cache pool
# ceph osd tier add rbd rbd.cache
# ceph osd tier cache-mode rbd.cache writeback
# ceph osd tier set-overlay rbd rbd.cache
5. 设置cache pool相关参数
参数含义请参考官网
# ceph osd pool set rbd.cache hit_set_type bloom
# ceph osd pool set rbd.cache hit_set_count 1
# ceph osd pool set rbd.cache hit_set_period 1800
# ceph osd pool set rbd.cache target_max_bytes 30000000000
# ceph osd pool set rbd.cache min_read_recency_for_promote 1
# ceph osd pool set rbd.cache min_write_recency_for_promote 1
# ceph osd pool set rbd.cache cache_target_dirty_ratio .4
# ceph osd pool set rbd.cache cache_target_dirty_high_ratio .6
# ceph osd pool set rbd.cache cache_target_full_ratio .8
6. 参考文档
【CACHE POOL】http://docs.ceph.com/docs/master/dev/cache-pool/
