On Tue, 18 Apr 2017, myoungwon oh wrote:
> Hi sage
>
> I am refactoring the source code in order to support the extensible
> tier (support redirect, dedup, external system)
>
> I have a few question.
>
> 1. My understanding is that base pool contains all metadata for all
> objects (do not evicted), and dedup pool or external systems contain
> the object data.
> Therefore, The big difference between the cache tier and the
> extensible tier is whether base pool contains metadata (such as
> object_info_t ) or not. Am i wrong?
Yeah. The base pool effectively becomes and index for everything.
> 2. Do you think the extensible tier should belong to cache_mode_t (in
> maybe_handle_cache_detail()) ? or is it better to work independently
> from cache tier.
It should be independent of the cache tiering. We should probably use the
tier_of and tiers fields in pg_pool_t but not cache_mode.
> 3. Regarding promotion object and flushing work, I think start_copy() (in
> promote_object()) and start_fush() can be reused in a simple
> redirection case ("the object is in that other pool"), if we modify
> the object (only metadata) is not evicted (removed). Is this right
> way?
Yes!
I suggest focusing on step 1 being the simple redirection tiering case (no
dedup) since it'll be tricky enough getting that part right.
Thanks!
sage
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