Answering to myself, I found the reason for 2147483647: it's documented as a failure to find enough OSD (missing OSDs). And it is normal as I selected different hosts for the 15 OSDs but I have only 12 hosts! I'm still interested by an "expert" to confirm that LRC k=9, m=3, l=4 configuration is equivalent, in terms of redundancy, to a jerasure configuration with k=9, m=6. Michel Le 04/04/2023 à 15:26, Michel Jouvin a écrit :
Hi,
As discussed in another thread (Crushmap rule for multi-datacenter erasure coding), I'm trying to create an EC pool spanning 3 datacenters (datacenters are present in the crushmap), with the objective to be resilient to 1 DC down, at least keeping the readonly access to the pool and if possible the read-write access, and have a storage efficiency better than 3 replica (let say a storage overhead <= 2).
In the discussion, somebody mentioned LRC plugin as a possible jerasure alternative to implement this without tweaking the crushmap rule to implement the 2-step OSD allocation. I looked at the documentation (https://docs.ceph.com/en/latest/rados/operations/erasure-code-lrc/) but I have some questions if someone has experience/expertise with this LRC plugin.
I tried to create a rule for using 5 OSDs per datacenter (15 in total), with 3 (9 in total) being data chunks and others being coding chunks. For this, based of my understanding of examples, I used k=9, m=3, l=4. Is it right? Is this configuration equivalent, in terms of redundancy, to a jerasure configuration with k=9, m=6?
The resulting rule, which looks correct to me, is:
--------
{ "rule_id": 6, "rule_name": "test_lrc_2", "ruleset": 6, "type": 3, "min_size": 3, "max_size": 15, "steps": [ { "op": "set_chooseleaf_tries", "num": 5 }, { "op": "set_choose_tries", "num": 100 }, { "op": "take", "item": -4, "item_name": "default~hdd" }, { "op": "choose_indep", "num": 3, "type": "datacenter" }, { "op": "chooseleaf_indep", "num": 5, "type": "host" }, { "op": "emit" } ] }
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Unfortunately, it doesn't work as expected: a pool created with this rule ends up with its pages active+undersize, which is unexpected for me. Looking at 'ceph health detail` output, I see for each page something like:
pg 52.14 is stuck undersized for 27m, current state active+undersized, last acting [90,113,2147483647,103,64,147,164,177,2147483647,133,58,28,8,32,2147483647]
For each PG, there is 3 '2147483647' entries and I guess it is the reason of the problem. What are these entries about? Clearly it is not OSD entries... Looks like a negative number, -1, which in terms of crushmap ID is the crushmap root (named "default" in our configuration). Any trivial mistake I would have made?
Thanks in advance for any help or for sharing any successful configuration?
Best regards,
Michel _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io