| [smila-dev] Sharing the same persistence storage (xmlstorage & binary) between different cluster nodes |
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Hi,
Here are few remarks based on the discussion with
Dmitry, who wanted to test clustering scenario with multiple blackboards, when
blackboards running on separate nodes needs to share the same data (same
persistence storage).
Currently no persistence service (xml and binary)
support this test scenario (where the stored data must be shared between
separate cluster nodes).
1. Binary Storage Service
Through the new concept of Binary storage it will
be possible to achieve this feature, by applying the appropriate configuration
(http://wiki.eclipse.org/SMILA/Project_Concepts/Binary_Storage#Cluster_configuration -
page is under construction)
2. XmlStorage Service
The Oracle Berkeley DB Xml does not support well
remotely environment (it is an embedded database architecture); The BDB Xml
community discourage setting the environment in remote file system. Also this
depends on the operating system where the environment is located.
"When Berkeley
DB database environment shared memory regions are backed by the file system, it
is a common application error to create database environments backed by remote
file systems such as the Network File System (NFS), Windows network shares
(SMB/CIFS) or the Andrew File System (AFS). Remote filesystems rarely support
mapping files into process memory, and even more rarely support correct
semantics for mutexes if the mapping succeeds. For this reason, we recommend
database environment directories be created in a local
filesystem."
So, it looks like for the remote situations, a
number of constraints needs to be met so the remote case work with BDB Xml
environments.
Based on this, following solutions (for Oracle
Berkeley DB Xml) are available in case of node clusters needs to share the same
XML persistence storage (BDB Xml environment):
1. at least we can try how the BDB Xml behaves in
remote situations for SMILA (we will need to test on different os)
2. an extra layer needs to be developed in
order to "fix" the embedded database architecture and to solve the remote calls.
This layer will be located on the same node-machine as the BDB Xml environment,
so the calls to the BDB Xml native API are locally (this will make
the deploy/installation a bit complicated ...)
Feedback is very welcome.
Best Regards,
Marius
__________________________
Marius, CIMPEAN Project Manager Numerica SA
17 Cometei Str 400493 Cluj-Napoca, Romania Phone : +40 0364-101062
FAX : +40 0364-101034 |