What’s the aim to have soo big m number? How many servers are in this cluster? Istvan Szabo Senior Infrastructure Engineer --------------------------------------------------- Agoda Services Co., Ltd. e: istvan.szabo@xxxxxxxxx<mailto:istvan.szabo@xxxxxxxxx> --------------------------------------------------- On 2022. Feb 21., at 19:20, Eugen Block <eblock@xxxxxx> wrote: Email received from the internet. If in doubt, don't click any link nor open any attachment ! ________________________________ Hi, it really depends on the resiliency requirements and the use case. We have a couple of customers with EC profiles like k=7 m=11. The potential waste of space as Anthony already mentions has to be considered, of course. But with regards to performance we haven't heard any complaints yet, but those clusters I'm referring to are archives with no high performance requirements but rather high requiremnts regarding datacenter resiliency. Regards, Eugen Zitat von Anthony D'Atri <anthony.datri@xxxxxxxxx>: A couple of years ago someone suggested on the list wrote: 3) k should only have small prime factors, power of 2 if possible I tested k=5,6,8,10,12. Best results in decreasing order: k=8, k=6. All other choices were poor. The value of m seems not relevant for performance. Larger k will require more failure domains (more hardware). I suspect that K being a power of 2 aligns with sharding, for efficiency and perhaps even minimizing space wasted due to internal fragmentation. As K increases, one sees diminishing returns for incremental raw:usable ratio, so I would think that for most purposes aligning to a power of 2 wouldn’t have much of a downside. Depending on your workload, large values could result in wasted space, analagous to eg. the dynamics of tiny S3 objects vs a large min_alloc_size : https://docs.google.com/spreadsheets/d/1rpGfScgG-GLoIGMJWDixEkqs-On9w8nAUToPQjN8bDI/edit#gid=358760253 I usually recommend a 2,2 profile as a safer alternative to replication with size=2, and 4,2 for additional space efficiency while blowing up the fault domain factor, rebuild overhead, etc. ymmocv On Feb 18, 2022, at 1:13 PM, ashley@xxxxxxxxxxxxxx wrote: I have read a few places its recommended to set K to a power of 2, is this still a “thing” with the latest/current CEPH Versions (quite a few of this articles are from years ago), or is a non power of 2 value equally as fine performance wise as a power of 2 now. Thanks _______________________________________________ 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 _______________________________________________ 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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