The problem is that "hammer" tunables (i.e. "optimal" in v0.94.x) are
incompatible with the kernel interfaces before Linux 4.1 (namely due
to straw2 buckets). To make use of the kernel interfaces in 3.13, I
believe you'll need "firefly" tunables.

--
Adam

On Sun, Nov 8, 2015 at 11:48 PM, Bogdan SOLGA <bogdan.so...@gmail.com> wrote:
> Hello Greg!
>
> Thank you for your advice, first of all!
>
> I have tried to adjust the Ceph tunables detailed in this page, but without
> success. I have tried both 'ceph osd crush tunables optimal' and 'ceph osd
> crush tunables hammer', but both lead to the same 'feature set mismatch'
> issue, whenever I tried to create a new RBD image, afterwards. The only way
> I could restore the proper functioning of the cluster was to set the
> tunables to default ('ceph osd crush tunables default'), which are the
> default values for a new cluster.
>
> So... either I'm doing something incompletely, or I'm doing something wrong.
> Any further advice on how to be able to use EC pools is highly welcomed.
>
> Thank you!
>
> Regards,
> Bogdan
>
>
> On Mon, Nov 9, 2015 at 12:20 AM, Gregory Farnum <gfar...@redhat.com> wrote:
>>
>> With that release it shouldn't be the EC pool causing trouble; it's the
>> CRUSH tunables also mentioned in that thread. Instructions should be
>> available in the docs for using older tunable that are compatible with
>> kernel 3.13.
>> -Greg
>>
>>
>> On Saturday, November 7, 2015, Bogdan SOLGA <bogdan.so...@gmail.com>
>> wrote:
>>>
>>> Hello, everyone!
>>>
>>> I have recently created a Ceph cluster (v 0.94.5) on Ubuntu 14.04.3 and I
>>> have created an erasure coded pool, which has a caching pool in front of it.
>>>
>>> When trying to map RBD images, regardless if they are created in the rbd
>>> or in the erasure coded pool, the operation fails with 'rbd: map failed: (5)
>>> Input/output error'. Searching the internet for a solution... I came across
>>> this page, which seems to detail exactly the same issue - a
>>> 'misunderstanding' between erasure coded pools and the 3.13 kernel (used by
>>> Ubuntu).
>>>
>>> Can you please advise on a fix for that issue? As we would prefer to use
>>> erasure coded pools, the only solutions which came into my mind were:
>>>
>>> upgrade to the Infernalis Ceph release, although I'm not sure the issue
>>> is fixed in that version;
>>>
>>> upgrade the kernel (on all the OSDs and Ceph clients) to the 3.14+
>>> kernel;
>>>
>>> Any better / easier solution is highly appreciated.
>>>
>>> Regards,
>>>
>>> Bogdan
>
>
>
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