Database Reference
In-Depth Information
FC is a SAN technology that carries data transfers between hosts and SAN storage at very high speeds. The
protocol supports 1 Gbps, 2 Gbps, 4 Gbps, and 16 Gbps (most recently) and maintains very low latency. The FC
protocol supports three different topologies: 1) connecting two devices in a point-to-point model; 2) An FC-arbitrated
loop connecting up to 128 devices; 3) FC switched fabric model. FC switched fabric is the most common topology for
Oracle RAC Database. The example in Figure
5-4
shows a configuration of two-node Oracle RAC connecting with Dell
Compellent SC8000 FC SAN storage using two FC switches.
RAC Node 1
RAC Node 2
HBA1-1
HBA1- 2
HBA 2-1
HBA2-2
Fibre Channel Switch SW2
Fibre Channel Switch SW1
FC Storage Controller FC2
FC Storage Controller: FC1
FC Storage Enclosure A
FC Storage Enclosure B
Fibre Connection
SAS Connection
Figure 5-4.
FC switch fabric topology
To provide highly available storage connections, each RAC host has two HBAs (Host Bus Adapter), each of which
connects to an FC switch through a fiber optical cable. Each FC switch connects to both FC storage controllers. To
increase the storage I/O bandwidth, each FC switch is connected to both FC controllers with two fiber cables. By using
FC switches, the number of servers that can connect to an FC storage is not restricted. And the distance between hosts
and storage can be up to 10 km. The components in the storage path such as HBAs, fiber optical cables, FC switches,
and the storage controllers are very robust and capable of providing highly efficient and reliable data transfer between
the server hosts and the storage. The FC storage controller can also connect to multiple storage enclosures. These
storage enclusures are connected by daisy-chained SAS cables. The physical links between the storage controllers and
the storage enclosures use SAS cables.
Figure
5-3
shows a configuration with two enclosures connected to two storage controllers. It is also possible to
add more storage enclosures. Storage vendors usually specify the maximum number of storage enclosures that their
controllers can support. Adding multiple storage enclosures allows you to add more disk spindles to the storage. For
example, if one enclosure holds 24 disks, two enclosures can hold up to 48 disks. You also can put disks of different
speeds in different enclosures. For example, to improve storage I/O performance, you can put SSDs in one enclosure
and 15K rpm hard disks in another enclosure. Today, many SAN storage vendors provide some kind of storage tiering
