Re: why not add (offset,len) to pglog

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Hi, Dong Wu,

1. As I currently work for other things, this proposal is abandon for
a long time
2. This is a complicated task as we need to consider a lots such as
(not just for writeOp, as well as truncate, delete) and also need to
consider the different affects for different backends(Replicated, EC).
3. I don't think it is good time to redo this patch now, since the
BlueStore and Kstore  is inprogress, and I'm afraid to bring some
side-effect.  We may prepare and propose the whole design in next CDS.
4. Currently, we already have some tricks to deal with recovery (like
throttle the max recovery op, set the priority for recovery and so
on). So this kind of patch may not solve the critical problem but just
make things better, and I am not quite sure that this will really
bring a big improvement. Based on my previous test, it works
excellently on slow disk (say hdd), and also for a short-time
maintaining. Otherwise, it will trigger the backfill process.  So wait
for Sage's opinion @sage

If you are interest on this, we may cooperate to do this.

Regards
Ning Yao


2015-12-25 14:23 GMT+08:00 Dong Wu <archer.wudong@xxxxxxxxx>:
> Thanks, from this pull request I learned that this issue is not
> completed, is there any new progress of this issue?
>
> 2015-12-25 12:30 GMT+08:00 Xinze Chi (信泽) <xmdxcxz@xxxxxxxxx>:
>> Yeah, This is good idea for recovery, but not for backfill.
>> @YaoNing have pull a request about this
>> https://github.com/ceph/ceph/pull/3837 this year.
>>
>> 2015-12-25 11:16 GMT+08:00 Dong Wu <archer.wudong@xxxxxxxxx>:
>>> Hi,
>>> I have doubt about pglog, the pglog contains (op,object,version) etc.
>>> when peering, use pglog to construct missing list,then recover the
>>> whole object in missing list even if different data among replicas is
>>> less then a whole object data(eg,4MB).
>>> why not add (offset,len) to pglog? If so, the missing list can contain
>>> (object, offset, len), then we can reduce recover data.
>>> _______________________________________________
>>> ceph-users mailing list
>>> ceph-users@xxxxxxxxxxxxxx
>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>
>>
>>
>> --
>> Regards,
>> Xinze Chi
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