F.A.Q on LEXST-SEA
How Lexst-SEA works ?
Lexst-SEA connects many servers together, and let them working together, this group of servers forms a "cluster". If each data server(data node) store 25G data( circa 500,000 web pages), then 10 data nodes can store 250G(5,000,000 web pages).
Besides, workload on the whole system would be distributed to 10 nodes, it also solves the bottleneck of performance gracefully.
What is Master Node ?
Master Node is the nerve center of LEXST-SEA system, it controls all the nodes in the cluster, checks the status of each nodes from time to time at interval of a few seconds.
What is User Node ?
User node stores the database table info, and user informations.
What is LexstTomcatCall Node ?
LexstTomcatCall is a Tomcat Web server, it accepts searching requests, assigns the searching order to each data node, and returns the result to user.
LexstTomcatCall node also accepts the data sent from "crawlers" and save data to data nodes.
What is Data Node?
Data nodes are the server where data store.
What is paritioning ?
LEXST-SEA divides the data into many parts, each node store one part which is "partitioning technology". Tthe bigger data volumn grows, the more partition(nodes) needed.
What is Standby Node ?
Standby Nodes has the identical data to their respective primary Nodes, they keep checking if the primary nodes are working properly, and keep the data same to primary nodes. When a primary nodes stop working, it would be kicked out, and its standby node would upgrades to a "primary node", the whole system would work properly without interruption.
There are 3 kind of standby nodes: Standby Data Nodes, Standby User Nodes, Standy Master Node.
Why LexstTomcatCall node has no standby node ?
Lexst-SEA allows multiple LexstTomcatCall nodes in the cluster, each LexstTomcatCall node are independent, ie, they working parallelly.
To prevent from halt of whole system, you need deploy more than one LexstTomcatCall node.
How standby node synchronize the data ?
You need not do anything, standby nodes would automatically do their job.
What is Idle Node ?
An idle node actually is a blank node without any data, the system would wake up idle node in following 2 situations:
1.The disk space is nearly full, or the data volumn would exceeding the space limit soon. The idle node upgrades to a data node, the system would partition the data and store new generated data into this new data node.
2.If a primary node has no standby nodes, the system would let an idle node to become a standby node, if there is any idle node in the cluster.
There are 3 kind of Idle nodes: Idle Data Nodes, Idle User Nodes, nodes. If you start the node as a data node, then it is an Idle data node. If you start the node as a user node, it woudl become an idle user node.
How many pages each node should store ?
It depends on the capacity of your hardware.
Typically each node store 500,000 pages,presuming the node is a Pentium IV pc, with 512 RAM.
If your PCs(servers) are much powerful, you can store more data (pages) on each node.
On other aspect, you should also take it into consideration that how many concurrent searches would take place.
How many Nodes you need ?
It depends on how big your data volumn is, and the capacity of your hardware. here is an example below:
If each node store 500,000 pages, and the planed data volumn is 2,000,000 pages. Then you need 4 primary data nodes, 4 standby data nodes.
Besides, you need one user node and one LexstTomcatCall node, and their standby nodes.
Then totally you need buy a license of 8 nodes.
(The license does not limit the number of master node, log node and their standby nodes.)
F.A.Q on LEXST-Database Cluster
Can I use SQL in Lexst-Database-Cluster?
No, SQL is a little slow.
If not by SQL, How to search the data ?
Lexst-Database-cluster offers client interface and API.
Can I import my big table into LEXST-database-cluster?
Yes, of course.
I have a table with 1000 thousand rows, can LEXST-database-cluster help faster the searching ?
1,000,000 rows is not a big table for LEXST database.
How about the maintenance ?
In most case, you need not consider problem of maintenance, because LEXST do it for you.
I have only one server computer , can I install LEXST-Database-Cluster ?
Yes, all 6 nodes can be installed on one physical server.
How about if error occurs?
Lexst-Database-Cluster log every step of the system.
What language does LEXST-Database-Cluster support?
Any language theoretically,if you ensure your platform can code and de-code your particular language.
What happens if master node fails ?
Lexst-Cluster alerts, a standby master node would take the role.
How about if data grows too fast and disk space is not enough ?
A Standby node or an idle node would be chosen to store.