Hi,

On Wed, 22 Oct 2014 20:05:48 +0000 (UTC) James wrote:
> Hello,
> 
> So looking at the package sys-cluster/ceph, I see these flags:
> cryptopp debug fuse gtk +libaio libatomic +nss radosgw static-libs tcmalloc
> xfs zfs   No specific flags for btrfs?

Ceph is optimized for btrfs by design, it has no configure options
to enable or disable btrfs-related stuff:
https://github.com/ceph/ceph/blob/master/configure.ac
No configure option => no use flag.
 
> ceph-0.67.9 is marked stable, while 0.67.10 and  0.80.5 are marked
> (yellow) testing and *9999 is marked (red) masked. So what version
> would anyone recommend, with what flags?  [1]

Just use the latest (0.80.7 ATM). You may just nerame and rehash
0.80.5 ebuild (usually this works fine). Or you may stay with
0.80.5, but with fewer bug fixes.
 
>  Ceph will be the DFS on top of a (3) node mesos+spark cluster. 
> btrfs is being  set up with 2 disks in raid 1 on each system. Btrfs
> seems to be keenly compatible with ceph [2].

If raid is supposed to be read more frequently than written to,
then my favourite solution is raid-10-f2 (2 far copies, perfectly
fine for 2 disks). This will give you read performance of raid-0 and
robustness of raid-1. Though write i/o will be somewhat slower due
to more seeks.

Also it depends on workload: if you'll have a lot of independent
read requests, raid-1 will be fine too. But for large read i/o from
a single or few clients raid-10-f2 is the best imo.

> Guidance and comments, warmly requested,
> James
> 
> 
> [1] 
> http://ceph.com/docs/v0.78/rados/configuration/filesystem-recommendations/
> 
> [2] http://ceph.com/docs/master/release-notes/#v0-80-firefly

Best regards,
Andrew Savchenko