Glossary - Cassandra: The Definitive Guide - page 308

The advantages of SEDA are higher concurrency and better management of CPU, disk, and
network resources.

You can read more about SEDA as it was originally proposed by Matt Welsh, David Culler,
and Eric Brewer at http://www.eecs.harvard.edu/~mdw/proj/seda .

See also Stage .

Seed N d Node

A seed is a node that already exists in a Cassandra cluster and is used by newly added nodes
to get up and running. The newly added node can start gossiping with the seed node to get
state information and learn the topology of the node ring. There may be many seeds in a
cluster.

Slliice

This is a type of read query. Use get_slice() to query by a single column name or a range
of column names. Use get_range_slice() to return a subset of columns for a range of
keys.

Sniittch
A snitchis Cassandra's way of mapping a node to a physical location in the network. It helps
determine the location of a node relative to another node in order to assist with discovery and
ensure efficient request routing. There are different kinds of snitches. The EndpointSnitch
(or RackInferringSnitch ), for instance, determines whether two nodes are in the same
data center or the same rack. Its strategy for doing so is essentially to guess at the relative
distance of two nodes in a data center and rack based on reading the second and third octets
of their IP addresses.

The DataCenterEndpointSnitch allows you to specify IP subnets for racks, grouped by
which data center the racks are in.
The PropertyFileSnitch allows you to map IP addresses to rack and data centers in a
properties file called cassandra-rack.properties.
The snitch strategy classes can be found in the org.apache.cassandra.locator package.

Sparse
In the relational model, every data type (table) must have a value for every column, even if
that value is sometimes null . Cassandra, on the other hand, represents a sparse or “schema-
free” data model, which means that rows may have values for as many or as few of the
defined columns as you like. This allows for a degree of efficiency. For example, consider a