Dima, 1) Easy to understand for users AI 2.x: cluster -> cache group -> cache -> table AI 3.x: cluster -> cache(==table)
2) Fine grained cache management - MVCC on/off per-cache - WAL mode on/off per-cache - Data size per-cache 3) Performance: - Efficient scans are not possible with cache groups - Efficient destroy/DROP - O(N) now, O(1) afterwards "Huge refactoring" is not precise estimate. Let's think on how to do that instead of how not to do :-) On Tue, Apr 10, 2018 at 11:41 AM, Dmitriy Setrakyan <dsetrak...@apache.org> wrote: > Vladimir, sounds like a huge refactoring. Other than "cache groups are > confusing", are we solving any other big issues with the new proposed > approach? > > (every time we try to refactor rebalancing, I get goose bumps) > > D. > > On Tue, Apr 10, 2018 at 1:32 AM, Vladimir Ozerov <voze...@gridgain.com> > wrote: > > > Igniters, > > > > Cache groups were implemented for a sole purpose - to hide internal > > inefficiencies. Namely (add more if I missed something): > > 1) Excessive heap usage for affinity/partition data > > 2) Too much data files as we employ file-per-partition approach. > > > > These problems were resolved, but now cache groups are a great source of > > confusion both for users and us - hard to understand, no way to configure > > it in deterministic way. Should we resolve mentioned performance issues > we > > would never had cache groups. I propose to think we would it take for us > to > > get rid of cache groups. > > > > Please provide your inputs to suggestions below. > > > > 1) "Merge" partition data from different caches > > Consider that we start a new cache with the same affinity configuration > > (cache mode, partition number, affinity function) as some of already > > existing caches, Is it possible to re-use partition distribution and > > history of existing cache for a new cache? Think of it as a kind of > > automatic cache grouping which is transparent to the user. This would > > remove heap pressure. Also it could resolve our long-standing issue with > > FairAffinityFunction when tow caches with the same affinity configuration > > are not co-located when started on different topology versions. > > > > 2) Employ segment-extent based approach instead of file-per-partition > > - Every object (cache, index) reside in dedicated segment > > - Segment consists of extents (minimal allocation units) > > - Extents are allocated and deallocated as needed > > - *Ignite specific*: particular extent can be used by only one partition > > - Segments may be located in any number of data files we find convenient > > With this approach "too many fsyncs" problem goes away automatically. At > > the same time it would be possible to implement efficient rebalance still > > as partition data will be split across moderate number of extents, not > > chaotically. > > > > Once we have p.1 and p.2 ready cache groups could be removed, couldn't > > they? > > > > Vladimir. > > >
