Hi, Paranay,
The logic of why IGFS does not have implemented CacheStore is that it aims
different goals.
Please see https://apacheignite-fs.readme.io/docs/in-memory-file-system for
general IGFS concepts: it has both "native" and Hadoop API , both these are
file-system like APIs. As a persistent layer the underlying secondary file
system is used. 
So, IGFS is designed with the "in-memory file system" being the central
concept, distributed cache is just its implementation.
IGFS is implemented using 2 caches , and  the mapping between files and K-V
pairs in caches is not trivial.
In contrast, CacheStore is used to load and persist caches , when (1) cache
is central concept of the task, and (2) when K-V  pairs more-or-less
directly map to the underlying storage (e.g. as in case of
org.apache.ignite.internal.processors.cache.H2CacheStoreStrategy.H2CacheStore).

Of course, you can add a CacheStore to the IGFS caches, but the question
arises, would an underlying secondary file system be better and cheaper
persistent layer?

p.s. HDFS is not read-only, it is read-write file system.



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