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I know writing to min_size as sync and size-min_size as async has been
discussed before and would help here. From what I understand required
a lot of code changes and goes against the strong consistency model of
Ceph. I'm not sure if it will be implemented although I do love this
idea to help against tail latency.
- ----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904  C70E E654 3BB2 FA62 B9F1


On Thu, Aug 27, 2015 at 12:48 PM, Jan Schermer  wrote:
> Don't kick out the node, just deal with it gracefully and without 
> interruption... if the IO reached the quorum number of OSDs then there's no 
> need to block anymore, just queue it. Reads can be mirrored or retried (much 
> quicker, because making writes idempotent, ordered and async is pretty hard 
> and expensive).
> If there's an easy way to detect unreliable OSD that flaps - great, let's 
> have a warning in ceph health.
>
> Jan
>
>> On 27 Aug 2015, at 20:43, Robert LeBlanc  wrote:
>>
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>> This has been discussed a few times. The consensus seems to be to make
>> sure error rates of NICs or other such metrics are included in your
>> monitoring solution. It would also be good to preform periodic network
>> tests like a full size ping with nofrag set between all nodes and have
>> your monitoring solution report that as well.
>>
>> Although I would like to see such a feature in Ceph, the concern is
>> that such a feature can quickly get out of hand and that something
>> else that is really designed for it should do it. I can understand
>> where they are coming from in that regard, but having Ceph kick out a
>> misbehaving node quickly is appealing as well (there would have to be
>> a way to specify that only so many nodes could be kicked out).
>> - ----------------
>> Robert LeBlanc
>> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904  C70E E654 3BB2 FA62 B9F1
>>
>>
>> On Thu, Aug 27, 2015 at 9:37 AM, Christoph Adomeit  wrote:
>>> Hello Ceph Users,
>>>
>>> yesterday I had a defective Gbic in 1 node of my 10 node ceph cluster.
>>>
>>> The Gbic was working somehow but had 50% packet-loss. Some packets went 
>>> through, some did not.
>>>
>>> What happend that the whole cluster did not service requests in time, there 
>>> were lots of timeouts and so on
>>> until the problem was isolated. Monitors and osds where asked for data but 
>>> did dot answer or answer late.
>>>
>>> I am wondering, here we have a highly redundant network setup and a highly 
>>> redundant piece of software, but a small
>>> network fault brings down the whole cluster.
>>>
>>> Is there anything that can be configured or changed in ceph so that 
>>> availability will become better in case of flapping networks ?
>>>
>>> I understand, it is not a ceph problem but a network problem but maybe 
>>> something can be learned from such incidents  ?
>>>
>>> Thanks
>>>  Christoph
>>> --
>>> Christoph Adomeit
>>> GATWORKS GmbH
>>> Reststrauch 191
>>> 41199 Moenchengladbach
>>> Sitz: Moenchengladbach
>>> Amtsgericht Moenchengladbach, HRB 6303
>>> Geschaeftsfuehrer:
>>> Christoph Adomeit, Hans Wilhelm Terstappen
>>>
>>> [email protected]     Internetloesungen vom Feinsten
>>> Fon. +49 2166 9149-32                      Fax. +49 2166 9149-10
>>> _______________________________________________
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>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
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