Texas Memory Systems RamSan-500 Connections, Installing a Host Bus Adaptor in the Host System

Chapter 3 – Connections

3.1 Installing a Host Bus Adaptor in the Host System

Host Bus Adapters (HBAs) provide an interface from the server’s PCI bus to Fibre Channel attached devices. HBAs are available from a variety of vendors. Before purchasing an HBA, ensure that it provides a driver for the Operating System (OS) version that you are using.

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 3.1.3, below, for details). Next, 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-500’s capabilities. A few different components can affect the maximum performance of the RamSan-500, including FC interfaces, Host Bus Adapters, PCI buses, and server CPU resources.

3.1.1 Fibre Channel Interface

Currently, the RamSan supports two Fibre Channel communication speeds: 2- and 4-gigabit. Accounting for encoding and overhead, these transfer rates allow data to be transmitted to the RamSan-500 at a half duplex rate of ~200 MB/s and ~400 MB/s, for 2- and 4-gigabit, respectively. 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-gigabit HBA):

( Smaller usage percentage / Larger ) x 400MB/s + 400MB/s

For example, to calculate a data usage pattern with 66% reads and

33% writes:

( 33 / 66 ) x 400 + 400 = 600 MB/s

Many applications require storage bandwidth that exceeds what a single FC connection can provide. To accommodate this situation, we provide up to 8 FC ports per RamSan-500, each of which can supply the bandwidth described above. Using multiple Fibre Channel

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