Le vendredi 23 mars 2018 à 12:14 +0100, Ilya Dryomov a écrit :
> On Fri, Mar 23, 2018 at 11:48 AM,  <c...@jack.fr.eu.org> wrote:
> > The stock kernel from Debian is perfect
> > Spectre / meltdown mitigations are worthless for a Ceph point of
> > view,
> > and should be disabled (again, strictly from a Ceph point of view)

I know that Ceph itself don't need this, but the cpeh client machines,
specially those hosting VMs or mùore diverse code, should have those
mitigations.

> > If you need the luminous features, using the userspace
> > implementations
> > is required (librbd via rbd-nbd or qemu, libcephfs via fuse etc)

I'd rather use the faster kernel cephfs implementation instead of fuse,
specially with the Meltdown PTI mitigation (I guess fuse implies twice
the userland-to-kernel calls which are costly using PTI).
I don't have an idea yet re. RBD...

> luminous cluster-wide feature bits are supported since kernel 4.13.

This means that there are differences between 4.9 and 4.14 re. Ceph
features. I know that quota are not supported yet in any kernel, but I
don't use this...
Are there some performance/stability improvements in the kernel that
would justify using 4.14 instead of 4.9 ? I can't find any list
anywhere...
Since I'm building a new cluster, I'd rather choose the latest software
from the start if it's justified.

-- 
Nicolas Huillard
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