4
Connections
4.1
Installing a Host Bus/Channel Adapter in the
Host System
Host Bus Adapters (HBAs) provide an interface from the server’s PCI bus to Fibre Channel
attached devices. Host Channel Adapters (HCAs) provide an interface from the server’s PCI bus
to InfiniBand devices. HBAs and HCAs are available from a variety of vendors. Before purchasing
one, ensure that it provides a driver for the Operating System (OS) version that you are using.
In subsequent sections, the term HBA will be used to represent HCA or HBA interchangeably.
Before installing the HBA, consult your server’s documentation to determine which one of its PCI
slots is on the fastest and least congested PCI bus (see Section 4.1.3 below for details). In order
to install the HBA, first power down your server and place the HBA in this slot. Power on your
server and follow the instructions provided with the HBA to install the driver. It is generally a
good idea to check the HBA provider’s Web site to obtain the latest drivers and firmware for the
HBA. Updated drivers may include new features, improved performance, and minor bug fixes.
Troubleshooting Tip:
If you encounter any problems with the HBA, the first step in the debugging process is
verifying that you are using the latest driver and firmware.
The speed of the server and network interface ultimately limit the RamSan-810’s capabilities. A
few different components can affect the maximum performance of the RamSan-810, including
FC/IB interfaces, Host Bus Adapters, PCI buses, and server CPU resources.
4.1.1
Fibre Channel Interface
Currently, the RamSan-810 supports Fibre Channel communication speeds of 2-Gb, 4-Gb, or
8-Gb per second. Accounting for encoding and overhead, the 4-Gb/sec transfer rate allows data
to be transmitted to the RamSan-810 at a half duplex rate of approximately 400 MB/s. Fibre
Channel interfaces have separate read and write connections that allow a maximum data rate of
twice the half-duplex rate. To sustain the maximum full duplex rate, the data usage pattern of
the system must be 50% read and 50% write (due to the individual half duplex limits). To find
the maximum for other data usage patterns, use the following formula (4-Gb HBA):
smaller usage percentage
larger
∗
400 MB/s + 400 MB/s
For example, to calculate a data usage pattern with 66% reads and 33% writes:
33
66
∗
400 + 400 = 600 MB/s
RamSan-810 User’s Manual
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Texas Memory Systems, Inc.
