It's pretty pointless to discuss erasure coding vs replicated without knowing how it'll be used. There are setups where erasure coding is faster than replicated. You do need to write less data overall, so if that's your bottleneck then erasure coding will be faster. Paul -- Paul Emmerich Looking for help with your Ceph cluster? Contact us at https://croit.io croit GmbH Freseniusstr. 31h 81247 München www.croit.io Tel: +49 89 1896585 90 On Tue, Dec 3, 2019 at 9:56 PM Nathan Fish <lordcirth@xxxxxxxxx> wrote: > > If k=8,m=3 is too slow on HDDs, so you need replica 3 and SSD DB/WAL, > vs EC 8,3 on SSD, then that's (1/3) / (8/11) = 0.45 multiplier on the > SSD space required vs HDDs. > That brings it from 6x to 2.7x. Then you have the benefit of not > needing separate SSDs for DB/WAL both in hardware cost and complexity. > SSDs will still be more expensive; but perhaps justifiable given the > performance, rebuild times, etc. > > If you only need cold-storage, then EC 8,3 on HDDs will be cheap. But > is that fast enough? > > On Tue, Dec 3, 2019 at 3:47 PM <jesper@xxxxxxxx> wrote: > > > > >> * Hardware raid with Battery Backed write-cache - will allow OSD to ack > > >> writes before hitting spinning rust. > > > > > > Disagree. See my litany from a few months ago. Use a plain, IT-mode HBA. > > > Take the $$ you save and put it toward building your cluster out of SSDs > > > instead of HDDs. That way you don’t have to mess with the management > > > hassles of maintaining and allocating external WAL+DB partitions too. > > > > These things are not really comparable - are they? Cost of SSD vs. HDD is > > still in the 6:1 favor of HHD's. Yes SSD would be great but not > > nessesarily affordable - or have I missed something that makes the math > > work ? > > > > -- > > Jesper > > _______________________________________________ > > 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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