We're currently putting data into our cephfs pool (cachepool in front of it as a caching tier), but the metadata pool contains ~50MB of data for 36 million files. If that were an accurate estimation, we'd have a metadata pool closer to ~140GB. Here is a ceph df detail: http://people.beocat.cis.ksu.edu/~mozes/ceph_df_detail.txt I'm not saying it won't get larger, I have no idea of the code behind it. This is just what it happens to be for us. -- Adam On Sat, Apr 25, 2015 at 11:29 AM, François Lafont <flafdivers@xxxxxxx> wrote: > Thanks Greg and Steffen for your answer. I will make some tests. > > Gregory Farnum wrote: > >> Yeah. The metadata pool will contain: >> 1) MDS logs, which I think by default will take up to 200MB per >> logical MDS. (You should have only one logical MDS.) >> 2) directory metadata objects, which contain the dentries and inodes >> of the system; ~4KB is probably generous for each? > > So one file in the cephfs generates one inode of ~4KB in the > "metadata" pool, correct? So that (number-of-files-in-cephfs) x 4KB > gives me an (approximative) estimation of the amount of data in the > "metadata" pool? > >> 3) Some smaller data structures about the allocated inode range and >> current client sessions. >> >> The data pool contains all of the file data. Presumably this is much >> larger, but it will depend on your average file size and we've not >> done any real study of it. > > -- > François Lafont > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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