16.4.4.10. MySQL Cluster SCI Transport Connections
[SCI] sections in the
config.ini file explicitly define SCI
(Scalable Coherent Interface) connections between cluster
nodes. Using SCI transporters in MySQL Cluster is supported
only when the MySQL-Max binaries are built using
--with-ndb-sci=/your/path/to/SCI.
The path should point to a
directory that contains at a minimum lib
and include directories containing SISCI
libraries and header files. (See
Section 16.8, “Using High-Speed Interconnects with MySQL Cluster” for more
information about SCI.)
In addition, SCI requires specialized hardware.
It is strongly recommended to use SCI Transporters only for
communication between ndbd processes. Note
also that using SCI Transporters means that the
ndbd processes never sleep. For this
reason, SCI Transporters should be used only on machines
having at least two CPUs dedicated for use by
ndbd processes. There should be at least
one CPU per ndbd process, with at least one
CPU left in reserve to handle operating system activities.
-
NodeId1, NodeId2
To identify a connection between two nodes it is necessary
to provide node identifiers for each of them, as
NodeId1 and NodeId2.
-
Host1SciId0
This identifies the SCI node ID on the first Cluster node
(identified by NodeId1).
-
Host1SciId1
It is possible to set up SCI Transporters for failover
between two SCI cards which then should use separate
networks between the nodes. This identifies the node ID
and the second SCI card to be used on the first node.
-
Host2SciId0
This identifies the SCI node ID on the second Cluster node
(identified by NodeId2).
-
Host2SciId1
When using two SCI cards to provide failover, this
parameter identifies the second SCI card to be used on the
second node.
-
SharedBufferSize
Each SCI transporter has a shared memory segment used for
communication between the two nodes. Setting the size of
this segment to the default value of 1MB should be
sufficient for most applications. Using a smaller value
can lead to problems when performing many parallel
inserts; if the shared buffer is too small, this can also
result in a crash of the ndbd process.
-
SendLimit
A small buffer in front of the SCI media stores messages
before transmitting them over the SCI network. By default,
this is set to 8KB. Our benchmarks show that performance
is best at 64KB but 16KB reaches within a few percent of
this, and there was little if any advantage to increasing
it beyond 8KB.
-
SendSignalId
To trace a distributed message it is necessary to identify
each message uniquely. When this parameter is set to
Y, message IDs are transported over the
network. This feature is disabled by default.
-
Checksum
This parameter is a boolean value, and is disabled by
default. When Checksum is enabled,
checksums are calculated for all messages before they are
placed in the send buffer. This feature prevents messages
from being corrupted while waiting in the send buffer. It
also serves as a check against data being corrupted during
transport.
