> 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? Ok, I understand. We have a "hot" fraction of our dataset - and 10GB cache on all 113 HDD ~1TB effective read-cache - and then writes hitting the battery-backed write-cache - this can overspill and when hitting "cold" data performance varies. But the read/write amplification of EC is still un-manageable in pratice on HDD with an active dataset. -- Jesper _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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