The store module allows you to control how index data is stored and accessed on disk.
There are different file system implementations or storage types. By default, Elasticsearch will pick the best implementation based on the operating environment.
This can be overridden for all indices by adding this to the
config/elasticsearch.yml
file:
index.store.type: niofs
It is a static setting that can be set on a per-index basis at index creation time:
PUT /my_index { "settings": { "index.store.type": "niofs" } }
This is an expert-only setting and may be removed in the future.
The following sections lists all the different storage types supported.
fs
hybridfs
on all
supported systems but is subject to change.
simplefs
SimpleFsDirectory
) using a random access file.
This implementation has poor concurrent performance (multiple threads
will bottleneck). It is usually better to use the niofs
when you need
index persistence.
niofs
NIOFSDirectory
) using NIO. It allows multiple threads to read
from the same file concurrently. It is not recommended on Windows
because of a bug in the SUN Java implementation.
mmapfs
MMapDirectory
) by mapping a file into memory (mmap). Memory
mapping uses up a portion of the virtual memory address space in your
process equal to the size of the file being mapped. Before using this
class, be sure you have allowed plenty of
virtual address space.
hybridfs
hybridfs
type is a hybrid of niofs
and mmapfs
, which chooses the best
file system type for each type of file based on the read access pattern.
Currently only the Lucene term dictionary, norms and doc values files are
memory mapped. All other files are opened using Lucene NIOFSDirectory
.
Similarly to mmapfs
be sure you have allowed plenty of
virtual address space.
You can restrict the use of the mmapfs
and the related hybridfs
store type
via the setting node.store.allow_mmap
. This is a boolean setting indicating
whether or not memory-mapping is allowed. The default is to allow it. This
setting is useful, for example, if you are in an environment where you can not
control the ability to create a lot of memory maps so you need disable the
ability to use memory-mapping.