On Mon, May 19, 2014 at 4:05 AM, Florent B <florent at coppint.com> wrote: > On 05/19/2014 12:40 PM, Wido den Hollander wrote: >> On 05/19/2014 12:31 PM, Florent B wrote: >>> Hi all, >>> >>> I use CephFS and I am wondering what does "metadata" pool contains >>> exactly ? >>> >> >> It contains the directory structure of your filesystem >> >>> Its size is growing (multiple GB). >>> >>> It seems that it stores all operations occurring in CephFS, but is it >>> totally necessary ? >>> >> >> It doesn't store all operations, but it stores all the metadata like >> directories, owners, file sizes, but not the contents of the files. > > It really seems to contain more than that. In our previous FS (MooseFS), > metadata was around 600MB for more files than we have on CephFS (which > metadata is around 3GB) ! That's really strange... It also contains per-MDS journals, which can get reasonably large. And just to clarify, when you restart an MDS it does not need to read *all* the metadata in the pool; it will initially read in the still-necessary parts of the journal and then will page in the rest of the structure as needed by subsequent client requests. -Greg Software Engineer #42 @ http://inktank.com | http://ceph.com
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