Hi Patrick, If your hardware is new and you are confident in the support of your hardware and can consider future expansion, you can possibly start with a k=3 and m=2. It is true that we generally prefer to divide (k) the data by an exponent 2, but k=3 does the job Be careful, it is difficult/painful to change profiles later (need data migration). ________________________________________________________ Cordialement, *David CASIER* ________________________________________________________ Le mar. 5 déc. 2023 à 12:35, Patrick Begou < Patrick.Begou@xxxxxxxxxxxxxxxxxxxxxx> a écrit : > Ok, so I've misunderstood the meaning of failure domain. If there is no > way to request using 2 osd/node and node as failure domain, with 5 nodes > k=3+m=1 is not secure enough and I will have to use k=2+m=2, so like a > raid1 setup. A little bit better than replication in the point of view of > global storage capacity. > > Patrick > > Le 05/12/2023 à 12:19, David C. a écrit : > > Hi, > > To return to my comparison with SANs, on a SAN you have spare disks to > repair a failed disk. > > On Ceph, you therefore need at least one more host (k+m+1). > > If we take into consideration the formalities/delivery times of a new > server, k+m+2 is not luxury (Depending on the growth of your volume). > > ________________________________________________________ > > Cordialement, > > *David CASIER* > > ________________________________________________________ > > > > Le mar. 5 déc. 2023 à 11:17, Patrick Begou < > Patrick.Begou@xxxxxxxxxxxxxxxxxxxxxx> a écrit : > >> Hi Robert, >> >> Le 05/12/2023 à 10:05, Robert Sander a écrit : >> > On 12/5/23 10:01, duluxoz wrote: >> >> Thanks David, I knew I had something wrong :-) >> >> >> >> Just for my own edification: Why is k=2, m=1 not recommended for >> >> production? Considered to "fragile", or something else? >> > >> > It is the same as a replicated pool with size=2. Only one host can go >> > down. After that you risk to lose data. >> > >> > Erasure coding is possible with a cluster size of 10 nodes or more. >> > With smaller clusters you have to go with replicated pools. >> > >> Could you explain why 10 nodes are required for EC ? >> >> On my side, I'm working on building my first (small) Ceph cluster using >> E.C. and I was thinking about 5 nodes and k=4 m=2. With a failure domain >> on host and several osd by nodes, in my mind this setup may run degraded >> with 3 nodes using 2 distincts osd by node and the ultimate possibility >> to loose an additional node without loosing data. Of course with >> sufficient free storage available. >> >> Am I totally wrong in my first ceph approach ? >> >> Patrick >> _______________________________________________ >> ceph-users mailing list -- ceph-users@xxxxxxx >> To unsubscribe send an email to ceph-users-leave@xxxxxxx >> > > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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