Re: EC pool only for hdd

[Eugen Block <eblock@xxxxxx>]

Of course it's possible. You can either change this rule by extracting  
the crushmap, decompiling it, editing the "take" section, compile it  
and inject it back into the cluster. Or you simply create a new rule  
with the class hdd specified and set this new rule for your pools. So  
the first approach would be:

1. ceph osd getcrushmap -o crushmap.bin
2. crushtool -d crushmap.bin -o crushmap.txt
3. open crushmap.txt with the editor of your choice, replace

        step take default
with:
        step take default class hdd

and save the file.

4. crushtool -c crushmap.txt -o crushmap.new
5. test it with crushtool:

crushtool -i crushmap.new --test --rule 1 --num-rep 5 --show-mappings | less
crushtool -i crushmap.new --test --rule 1 --num-rep 5  
--show-bad-mappings | less

You shouldn't have bad mappings if everything is okay. Inspect the  
result of --show-mappings to see if the OSDs match your HDD OSDs.

6. ceph osd setcrushmap -i crushmap.new

####

Alternatively, create a new rule if your EC profile(s) already have  
the correct crush-device-class set. If not, you can create a new one,  
but keep in mind that you can't change the k and m values for a given  
pool, so you need to ensure that you use the same k and m values:

ceph osd erasure-code-profile set ec-profile-k3m2 k=3 m=2  
crush-failure-domain=host crush-device-class=hdd

ceph osd crush rule create-erasure rule-ec-k3m2 ec-profile-k3m2

And here's the result:

ceph osd crush rule dump rule-ec-k3m2 | grep -A2 take
            "op": "take",
            "item": -2,
            "item_name": "default~hdd"

Regards,
Eugen

Zitat von Rok Jaklič <rjaklic@xxxxxxxxx>:

> Hi,
>
> is it possible to set/change following already used rule to only use hdd?
> {
>     "rule_id": 1,
>     "rule_name": "ec32",
>     "type": 3,
>     "steps": [
>         {
>             "op": "set_chooseleaf_tries",
>             "num": 5
>         },
>         {
>             "op": "set_choose_tries",
>             "num": 100
>         },
>         {
>             "op": "take",
>             "item": -1,
>             "item_name": "default"
>         },
>         {
>             "op": "chooseleaf_indep",
>             "num": 0,
>             "type": "host"
>         },
>         {
>             "op": "emit"
>         }
>     ]
> }
>
> Kind regards,
> Rok
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