On Mon, 10 Nov 2014, David Moreau Simard wrote: > Hi, > > It's easy to calculate the amount of "raw" storage vs "actual" storage on replicated pools. > Example with 4x 2TB disks: > - 8TB "raw" > - 4TB "usable" (when using 2 replicas) > > I understand how erasure coded pools reduces the overhead of storage required for data redundancy and resiliency and how it depends on the erasure coding profile you use. > > Do you guys have an easy way to figure out the amount of usable storage ? The 'ceph df' command now has a 'MAX AVAIL' column that factors in either the replication factor or erasure k/(k+m) ratio. It also takes into account the projected distribution of data across disks from the CRUSH rule and uses the 'first OSD to fill up' as the target. What it doesn't take into account is the expected variation in utilization or the 'full_ratio' and 'near_full_ratio' which will stop writes sometime before that point. sage _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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