Hi,
I am trying to create an EC pool on my SSD based OSDs
and will appreciate if someone clarify / provide advice about the following
- best K + M combination for 4 hosts one OSD per host
My understanding is that K+M< OSD but using K=2, M=1 does not provide any redundancy
( as soon as 1 OSD is down, you cannot write to the pool)
Am I right ?
- assigning crush_rule as per documentation does not seem to work
If I provide all the crush rule details when I create the EC profile, the PGs are being placed on SSD OSDs AND a crush rule is automatically create
Is that the right/new way of doing it ?
EXAMPLE
ceph osd erasure-code-profile set erasureISA crush-failure-domain=osd k=3 m=2 crush-root=ssds plugin=isa technique=cauchy crush-device-class=ssd
[root@osd01 ~]# ceph osd crush rule ls
replicated_rule
erasure-code
ssdrule
[root@osd01 ~]# ceph osd crush rule dump ssdrule
{
"rule_id": 2,
"rule_name": "ssdrule",
"ruleset": 2,
"type": 1,
"min_size": 1,
"max_size": 10,
"steps": [
{
"op": "take",
"item": -4,
"item_name": "ssds"
},
{
"op": "chooseleaf_firstn",
"num": 0,
"type": "host"
},
{
"op": "emit"
}
]
}
[root@osd01 ~]# ceph osd pool set test crush_rule 2
Error ENOENT: crush rule 2 does not exist
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