Oh, that's interesting - I didn't know that. Thanks. -- David Moreau Simard > On Nov 10, 2014, at 6:06 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote: > > 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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