[ceph-users] Re: Where has my capacity gone?

Hi George, If the amplification is indeed due to min_alloc_size, then I don't think that compression will help. My understanding is that compression is applied post-EC (and thus probably won't even activate due to the small chunks), and that the compressed bits will still be stored on disk in the same way as before (min_alloc_size still applies). More info here: https://www.suse.com/support/kb/doc/?id=000019629 It's possible, though, that turning on compression and tuning its settings could reduce the overall number of blocks allocated, which would compensate slightly for the amplification. To confirm that you'd have to analyze the object sizes of your data set. There are also pathological cases where perhaps most of your EC chunks are slightly over 64K and by forcing them to compress (they won't by default) you actually cut allocated blocks in half. Again, that would take analysis to determine. Josh