On Thu, Dec 17, 2015 at 2:06 PM, John Spray <jsp...@redhat.com> wrote: > On Thu, Dec 17, 2015 at 2:31 PM, Simon Hallam <s...@pml.ac.uk> wrote: >> Hi all, >> >> >> >> I’m looking at sizing up some new MDS nodes, but I’m not sure if my thought >> process is correct or not: >> >> >> >> CPU: Limited to a maximum 2 cores. The higher the GHz, the more IOPS >> available. So something like a single E5-2637v3 should fulfil this. > > No idea where you're getting the 2 core part. But a mid range CPU > like the one you're looking at is probably perfectly appropriate. As > you have probably gathered, the MDS will not make good use of large > core counts (though there are plenty of threads and various > serialisation/deserialisation parts can happen in parallel).
There's just not much that happens outside of the big MDS lock right now, besides journaling and some message handling. So basically two cores is all we'll be able to use until that happens. ;) > >> Memory: The more the better, as the metadata can be cached in RAM (how much >> RAM required is dependent on number of files?). > > Correct, the more RAM you have, the higher you can set mds_cache_size, > and the larger your working set will be. Note that "working set" there; it's only the active metadata you need to worry about when sizing things. I think at last count Zheng was seeing ~3KB of memory for each inode/dentry combo. -Greg _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
