Caspar, Thank you for your reply. I’m in all honesty still not clear on what value to use for min_size. From what I understand, it should be be set to the sum of k+m for erasure coded pools, as it is set by default.
Additionally, could you elaborate why m=2 would be able to sustain a node failure? As stated, we have 6 hosts containing 4 OSDs (so 24) total. What would m=2 achieve that m=1 would not? Kind regards Ziggy Maes DevOps Engineer CELL +32 478 644 354 SKYPE Ziggy.Maes [http://www.be-mobile.com/mail/bemobile_email.png]<http://www.be-mobile.com/> www.be-mobile.com<http://www.be-mobile.com> From: Caspar Smit <caspars...@supernas.eu> Date: Friday, 20 July 2018 at 13:36 To: Ziggy Maes <ziggy.m...@be-mobile.com> Cc: "ceph-users@lists.ceph.com" <ceph-users@lists.ceph.com> Subject: Re: [ceph-users] Default erasure code profile and sustaining loss of one host containing 4 OSDs Ziggy, The default min_size for your pool is 3 so losing ANY single OSD (not even host) will result in reduced data availability: https://patchwork.kernel.org/patch/8546771/ Use m=2 to be able to handle a node failure. Met vriendelijke groet, Caspar Smit Systemengineer SuperNAS Dorsvlegelstraat 13 1445 PA Purmerend t: (+31) 299 410 414 e: caspars...@supernas.eu<mailto:caspars...@supernas.eu> w: www.supernas.eu<http://www.supernas.eu> 2018-07-20 13:11 GMT+02:00 Ziggy Maes <ziggy.m...@be-mobile.com<mailto:ziggy.m...@be-mobile.com>>: Hello I am currently trying to find out if Ceph can sustain the loss of a full host (containing 4 OSDs) in a default erasure coded pool (k=2, m=1). We have currently have a production EC pool with the default erasure profile, but would like to make sure the data on this pool remains accessible even after one of our hosts fail. Since we have a very small cluster (6 hosts, 4 OSDs per host), I created a custom CRUSH rule to make sure the 3 chunks are spread over 3 hosts, screenshot here: https://gyazo.com/1a3ddd6895df0d5e0e425774d2bcb257 . Unfortunately, taking one node offline results in reduced data availability and incomplete PGs, as shown here: https://gyazo.com/db56d5a52c9de2fd71bf9ae8eb03dbbc . My question summed up: is it possible to sustain the loss of a host containing 4 OSDs using a k=2, m=1 erasure profile using a CRUSH map that spreads data over at least 3 hosts? If so, what am I doing wrong? I realize the documentation states that m equals the amount of OSDs that can be lost, but assuming a balanced CRUSH map is used I fail to see how this is required. Many thanks in advance. Kind regards Ziggy Maes DevOps Engineer [http://www.be-mobile.com/mail/bemobile_email.png]<http://www.be-mobile.com/> www.be-mobile.com<http://www.be-mobile.com> _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com<mailto:ceph-users@lists.ceph.com> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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