Thanks - so it appears that the advantage of the 3rd replica (relative to 2 replicas) has to do much more with recovering from two concurrent OSD failures than with inconsistencies found during deep scrub - would you agree?
Re: repair - do you mean the "repair" process during deep scrub - if yes, this is automatic - correct?
Or
Are you referring to the explicit manually initiated repair commands?
Thanks,
-Sudip
-----Original Message-----
From: Samuel Just [mailto:sam.just@xxxxxxxxxxx]
Sent: Thursday, July 10, 2014 10:50 AM
To: Chahal, Sudip
Cc: Christian Eichelmann; ceph-users at lists.ceph.com
Subject: Re: scrub error on firefly
Repair I think will tend to choose the copy with the lowest osd number which is not obviously corrupted. Even with three replicas, it does not do any kind of voting at this time.
-Sam
On Thu, Jul 10, 2014 at 10:39 AM, Chahal, Sudip <sudip.chahal at intel.com> wrote:
> I've a basic related question re: Firefly operation - would appreciate any insights:
>
> With three replicas, if checksum inconsistencies across replicas are found during deep-scrub then:
> a. does the majority win or is the primary always the winner and used to overwrite the secondaries
> b. is this reconciliation done automatically during deep-scrub or does each reconciliation have to be executed manually by the administrator?
>
> With 2 replicas - how are things different (if at all):
> a. The primary is declared the winner - correct?
> b. is this reconciliation done automatically during deep-scrub or does it have to be done "manually" because there is no majority?
>
> Thanks,
>
> -Sudip
>
>
> -----Original Message-----
> From: ceph-users [mailto:ceph-users-bounces at lists.ceph.com] On Behalf
> Of Samuel Just
> Sent: Thursday, July 10, 2014 10:16 AM
> To: Christian Eichelmann
> Cc: ceph-users at lists.ceph.com
> Subject: Re: [ceph-users] scrub error on firefly
>
> Can you attach your ceph.conf for your osds?
> -Sam
>
> On Thu, Jul 10, 2014 at 8:01 AM, Christian Eichelmann <christian.eichelmann at 1und1.de> wrote:
>> I can also confirm that after upgrading to firefly both of our
>> clusters (test and live) were going from 0 scrub errors each for
>> about
>> 6 Month to about 9-12 per week...
>> This also makes me kind of nervous, since as far as I know everything
>> "ceph pg repair" does, is to copy the primary object to all replicas,
>> no matter which object is the correct one.
>> Of course the described method of manual checking works (for pools
>> with more than 2 replicas), but doing this in a large cluster nearly
>> every week is horribly timeconsuming and error prone.
>> It would be great to get an explanation for the increased numbers of
>> scrub errors since firefly. Were they just not detected correctly in
>> previous versions? Or is there maybe something wrong with the new code?
>>
>> Acutally, our company is currently preventing our projects to move to
>> ceph because of this problem.
>>
>> Regards,
>> Christian
>> ________________________________
>> Von: ceph-users [ceph-users-bounces at lists.ceph.com]" im Auftrag von
>> "Travis Rhoden [trhoden at gmail.com]
>> Gesendet: Donnerstag, 10. Juli 2014 16:24
>> An: Gregory Farnum
>> Cc: ceph-users at lists.ceph.com
>> Betreff: Re: [ceph-users] scrub error on firefly
>>
>> And actually just to follow-up, it does seem like there are some
>> additional smarts beyond just using the primary to overwrite the
>> secondaries... Since I captured md5 sums before and after the
>> repair, I can say that in this particular instance, the secondary copy was used to overwrite the primary.
>> So, I'm just trusting Ceph to the right thing, and so far it seems
>> to, but the comments here about needing to determine the correct
>> object and place it on the primary PG make me wonder if I've been missing something.
>>
>> - Travis
>>
>>
>> On Thu, Jul 10, 2014 at 10:19 AM, Travis Rhoden <trhoden at gmail.com> wrote:
>>>
>>> I can also say that after a recent upgrade to Firefly, I have
>>> experienced massive uptick in scrub errors. The cluster was on
>>> cuttlefish for about a year, and had maybe one or two scrub errors.
>>> After upgrading to Firefly, we've probably seen 3 to 4 dozen in the
>>> last month or so (was getting 2-3 a day for a few weeks until the whole cluster was rescrubbed, it seemed).
>>>
>>> What I cannot determine, however, is how to know which object is busted?
>>> For example, just today I ran into a scrub error. The object has
>>> two copies and is an 8MB piece of an RBD, and has identical
>>> timestamps, identical xattrs names and values. But it definitely
>>> has a different
>>> MD5 sum. How to know which one is correct?
>>>
>>> I've been just kicking off pg repair each time, which seems to just
>>> use the primary copy to overwrite the others. Haven't run into any
>>> issues with that so far, but it does make me nervous.
>>>
>>> - Travis
>>>
>>>
>>> On Tue, Jul 8, 2014 at 1:06 AM, Gregory Farnum <greg at inktank.com> wrote:
>>>>
>>>> It's not very intuitive or easy to look at right now (there are
>>>> plans from the recent developer summit to improve things), but the
>>>> central log should have output about exactly what objects are
>>>> busted. You'll then want to compare the copies manually to
>>>> determine which ones are good or bad, get the good copy on the
>>>> primary (make sure you preserve xattrs), and run repair.
>>>> -Greg
>>>> Software Engineer #42 @ http://inktank.com | http://ceph.com
>>>>
>>>>
>>>> On Mon, Jul 7, 2014 at 6:48 PM, Randy Smith <rbsmith at adams.edu> wrote:
>>>> > Greetings,
>>>> >
>>>> > I upgraded to firefly last week and I suddenly received this error:
>>>> >
>>>> > health HEALTH_ERR 1 pgs inconsistent; 1 scrub errors
>>>> >
>>>> > ceph health detail shows the following:
>>>> >
>>>> > HEALTH_ERR 1 pgs inconsistent; 1 scrub errors pg 3.c6 is
>>>> > active+clean+inconsistent, acting [2,5]
>>>> > 1 scrub errors
>>>> >
>>>> > The docs say that I can run `ceph pg repair 3.c6` to fix this.
>>>> > What I want to know is what are the risks of data loss if I run
>>>> > that command in this state and how can I mitigate them?
>>>> >
>>>> > --
>>>> > Randall Smith
>>>> > Computing Services
>>>> > Adams State University
>>>> > http://www.adams.edu/
>>>> > 719-587-7741
>>>> >
>>>> > _______________________________________________
>>>> > ceph-users mailing list
>>>> > ceph-users at lists.ceph.com
>>>> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>>>> >
>>>> _______________________________________________
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>>>
>>>
>>
>>
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