Terracotta Discussion Forums (LEGACY READ-ONLY ARCHIVE)

We have configured ehcache.xml as follows
Code:

 <ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="ehcache.xsd"
       updateCheck="false"
       maxBytesLocalHeap="1G"
       maxBytesLocalOffHeap="4G"
       maxBytesLocalDisk="60G"
       >
 
       <defaultCache eternal="true" overflowToOffHeap="true" overflowToDisk="true" memoryStoreEvictionPolicy="LRU" />
       <cache name="demo1"></cache>
      <cache name="demo2"></cache>
 
 </ehcache>

Queries:-
1. Suppose we are adding elements in “demo1” cache and at certain point “demo1” Local Heap and Off-heap storages are full. Suppose there is an element E1 present only in Disk storage. If application calls get on “demo1” for E1, Fault occur for E1. Is it E1 copied from Disk to Local Heap? If yes then as Local Heap is full, Ehcache would evict an element E2 from Local Heap and then copy E4 to local Heap. Please confirm.

2. While copying E1 from Disk to local Heap, does Ehcache copy E1 to Off-heap as well?

3. Ehcache reserves 500m Local Heap each for “demo1” and “demo2”. Suppose “demo1” Local Heap is full but “Demo2” Local Heap is not full. If user try to add an element into “demo1”, Is there a configuration setting by which “Demo1” can use “Demo2” unutilized Local Heap?

4. We can increase Maximum Serialized Size of an Element by using “net.sf.ehcache.offheap.com.company.domain.State.config.idealMaxSegmentSize”. Suppose it’s value set to 30MB.
Is it the smallest amount of off heap that will be allocated? Does it mean that to store a 1MB object, BigMemory will allocate a 30MB chunk of memory and waste 29MB?

Some of the answers depend on the version you are using.

Can you specify your version?

bigmemory-go-4.1.0(ehcache-ee-2.8.0.jar)

Given the version 2.8.0 of ehcache enterprise:
1. Yes, but E2 would go to off-heap.

2. No

3. Ehcache does not split the memory between caches, rather the caches consumme memory from the common pool. There is no demo1 full vs demo2 not full, there is demo1 and demo2 in a 1GB pool, either full or not.

4. You should not use this setting unless faced with value storage errors. Default value is at 32MB. Space will not be wasted.

Hope this helps!