Database Reference
In-Depth Information
plication when compared to the heap size requirement on a 32-bit machine. Com-
pressed OOP options help to keep the heap size smaller on 64-bit machines.
(Read more about compressed OOPs on
http://docs.oracle.com/javase/7/docs/
It is generally suggested to run Cassandra on Oracle Java 6. Compressed OOPs
are supported and activated by default from Java SE Version 6u23+. For earlier
releases, you need to explicitly activate this by passing the
-
XX:+UseCompressedOops
flag.
•
Enable JNA
: Refer to
Chapter 4
,
Deploying a Cluster
, for the specifics of in-
stalling the JNA library for your operating system. JNA gives Cassandra access to
native OS libraries (shared libraries and DLLs). Cassandra uses JNA for off-heap
row cache that does not get swapped and in general gives favorable performance
results on reads and writes. If no JNA exists, Cassandra falls back to on-heap row
caching, which has a negative impact on performance. JNA also helps while tak-
ing backups; snapshots are created with help of JNA, which would have taken
much longer with
fork
and Java
exec
.
