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From "Raffaele P. Guidi" <>
Subject Re: Involvement as a developer
Date Wed, 19 Oct 2011 13:31:49 GMT
Sorry, Ashish, but I think there must be a misunderstanding: the map doesn't
contain the actual data, it is just the index to data itself, which is into
the off-heap memory. In fact it is a collection of Pointer objects, which
contain the offset and the lenght of the DirectBuffer that contains the
actual byte array. So: replicating the map (which is natively offered by
both hc and terracotta) means replicating the INDEX of the data, not data

Again: replication of the map(index) is one matter, distribution of the data
is a different question. I'm not proposing to use  terracotta or hazelcast
for their caching features but for their *clustering* features

On Wed, Oct 19, 2011 at 2:46 PM, Ashish <> wrote:

> On Wed, Oct 19, 2011 at 5:41 PM, Raffaele P. Guidi
> <> wrote:
> > Also, on replication/distribution, we have two distinct aspects:
> >
> >
> >   1. *map replication* - the pointers map has to be replicated to all
> nodes
> >   and each pointer have to contain also a reference to the node who
> "owns" the
> >   real data
> >   2. *communication between nodes* - once one node knows that one entry
> is
> >   contained in node "n" has to ask for it
> >
> >
> > The first point is easily covered by terracotta or hazelcast, while the
> > second one should be implemented using an RPC mechanism (Thrift or Avro
> are
> > both good choices). Another option is to cover also point 1 with a custom
> > replication built on top of the chosen RPC framework - of course this
> would
> > lead to another (do we really need it?) distributed map implementation.
> Disagree on this. Be it TC or Hazelcast, they shall cover both the points.
> Lets take an example of Terracotta. Its a Client-Server architecture
> with striping on Server side.
> Now if you choose TC (short for Terracotta), you got 3 options
> 1. Use DSO or Distributed Shared Object mode - needs instrumentation
> and other stuff, not recommended
> 2. Use Ehcache at back, and TC takes care Distributing data
> 3. Use Map via TC Toolkit
> TC will not let you know where its storing the key (which infact are
> stored in HA manner on Server Stripe). That's the beauty of TC. It
> does the faulting/flushing transparently to the user code.
> On Hazelcast side, it does allow to know where the key is, but the
> moment you use its client, it becomes transparent to you.
> IMHO, using any existing cache solution would complicate the user story.
> Distribution is a nice to have feature, and infact would lead to a
> wider adoption :)
> >
> > Keeping things like this is easy - of course making it
> efficient/performant
> > is a different story (i.e., should I keep a local cache of frequently
> > accessed items stored in other nodes? etc..).
> >
> > Ciao,
> >    R
> >
> thanks
> ashish

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