Re: Cache mode readforward mode will eat your babies?

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On Thu, Jun 8, 2017 at 3:47 PM, Christian Balzer <chibi@xxxxxxx> wrote:
> On Thu, 8 Jun 2017 15:29:05 +1000 Brad Hubbard wrote:
>
>> On Thu, Jun 8, 2017 at 3:10 PM, Christian Balzer <chibi@xxxxxxx> wrote:
>> > On Thu, 8 Jun 2017 14:21:43 +1000 Brad Hubbard wrote:
>> >
>> >> On Thu, Jun 8, 2017 at 1:06 PM, Christian Balzer <chibi@xxxxxxx> wrote:
>> >> >
>> >> > Hello,
>> >> >
>> >> > New cluster, Jewel, setting up cache-tiering:
>> >> > ---
>> >> > Error EPERM: 'readforward' is not a well-supported cache mode and may corrupt your data.  pass --yes-i-really-mean-it to force.
>> >> > ---
>> >> >
>> >> > That's new and certainly wasn't there in Hammer, nor did it whine about
>> >> > this when upgrading my test cluster to Jewel.
>> >> >
>> >> > And speaking of whining, I did that about this and readproxy, but not
>> >> > their stability (readforward has been working nearly a year flawlessly in
>> >> > the test cluster) but their lack of documentation.
>> >> >
>> >> > So while of course there is no warranty for anything with OSS, is there
>> >> > any real reason for the above scaremongering or is that based solely on
>> >> > lack of testing/experience?
>> >>
>> >> https://github.com/ceph/ceph/pull/8210 and
>> >> https://github.com/ceph/ceph/pull/8210/commits/90fe8e3d0b1ded6d14a6a43ecbd6c8634f691fbe
>> >> may offer some insight.
>> >>
>> > They do, alas of course immediately raise the following questions:
>> >
>> > 1. Where is that mode documented?
>>
>> It *was* documented by,
>> https://github.com/ceph/ceph/pull/7023/commits/d821acada39937b9dacf87614c924114adea8a58
>> in https://github.com/ceph/ceph/pull/7023 but was removed by
>> https://github.com/ceph/ceph/commit/6b6b38163b7742d97d21457cf38bdcc9bde5ae1a
>> in https://github.com/ceph/ceph/pull/9070
>>
>
> I was talking about proxy, which isn't AFAICT, nor is there a BIG bold red

That was hard to follow for me, in a thread titled "Cache mode
readforward mode will eat your babies?".

> statement in the release notes (or docs) for everybody to switch from
> (read)forward to (read)proxy.
>
> And the two bits up there have _very_ conflicting statements about what
> readproxy does, the older one would do what I want (at the cost of
> shuffling all through the cache-tier network pipes), the newer one seems
> to be actually describing the proxy functionality (no new objects i.e from
> writes being added).
>
> I'll be ready to play with my new cluster in a bit and shall investigate
> what does actually what.
>
> Christian
>
>> HTH.
>>
>> >
>> > 2. The release notes aren't any particular help there either and issues/PR
>> > talk about forward, not readforward as the culprit.
>> >
>> > 3. What I can gleam from the bits I found, proxy just replaces the forward
>> > functionality.  Alas what I'm after is a mode that will not promote reads
>> > to the cache, aka readforward. Or another set of parameters that will
>> > produce the same results.
>> >
>> > Christian
>> >
>> >> >
>> >> > Christian
>> >> > --
>> >> > Christian Balzer        Network/Systems Engineer
>> >> > chibi@xxxxxxx           Rakuten Communications
>> >> > _______________________________________________
>> >> > ceph-users mailing list
>> >> > ceph-users@xxxxxxxxxxxxxx
>> >> > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>> >>
>> >>
>> >>
>> >
>> >
>> > --
>> > Christian Balzer        Network/Systems Engineer
>> > chibi@xxxxxxx           Rakuten Communications
>>
>>
>>
>
>
> --
> Christian Balzer        Network/Systems Engineer
> chibi@xxxxxxx           Rakuten Communications



-- 
Cheers,
Brad
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