Differences between Ehcache 3 OffHeap storage and BigMemory

Question

In Ehcache 2.X offheap storage is available using Terracotta's BigMemory commercial product. However, since Ehcache 3 it seems offheap storage is free.

I wonder if BigMemory product has moved to Ehcache 3 and if they are different product, what are the differences between them?

Thanks,

References:

• Offheap storage in Ehcache 2.X using BigMemory: http://www.ehcache.org/documentation/2.8/get-started/storage-options.html
• Offheap storage in Ehcache 3: http://www.ehcache.org/documentation/3.0/caching-concepts.html#storage-tiers

Answer 1

BigMemory is the commercial name of the product that is Ehcache + Terracotta clustering + offheap memory and other enterprise only features such as security to name one.

Offheap is the name of the technology that allows to use memory in the java world which is not under the control of the garbage collector.

Offheap was open sourced by Terracotta in early 2015 which enabled to have again an open source clustering solution for Ehcache. This was the main feature of Ehcache 2.10.0 which worked with Terracotta server 4.3.0, which uses offheap for the server side storage.

Ehcache 2.x does not have the offheap feature available in open source. However, Ehcache 3.x does have it. The main reason for keeping that difference is around engineering resources and the will to promote newer versions of the library.

The underlying offheap implementation that was open sourced is effectively what has been used inside the Terracotta commercial products for a number of years and is thus a production tested library.

Note: I work for Terracotta on Ehcache and related libraries / products.

Answer 2

See the source code. I see Ehcache 3 uses Terracotta library internally which is licensed under Apache. Ehcache 3 offheap class . Terracota lib .

import org.terracotta.offheapstore.MetadataTuple;
import org.terracotta.offheapstore.Segment;
import org.terracotta.offheapstore.concurrent.AbstractConcurrentOffHeapCache;
import org.terracotta.offheapstore.pinning.PinnableSegment;
import org.terracotta.offheapstore.util.Factory;