IBM eX5 Implementation Guide

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Of all of the I/O adapters that can be installed on the server, the ServeRAID and 6 Gbps SAS

controllers, when managing solid-state drives (SSDs), are the only adapters that can

approach the theoretical limits of the x8 PCIe 2.0 slot. When you use SSD drives, connect no

more than 8 SSD drives to a single controller for the best performance of the SSD drives.

Only use x8 slots to host the controllers that manage your SSD drives (that is, not slot 4,

because it is an x4 slot).

A single ServeRAID controller managing a single 4-drive SAS hard disk drive (HDD) array will

function within the theoretical limits of an x4 PCIe slot. In this case, the mechanical nature of

the HDD drives will limit the maximum throughput of data that passes through the PCIe slot.

The dual-port 8 Gbs Fibre Channel, 10Gbs Ethernet, and 10 Gbs Converge Network

Adapters (CNAs) are all capable of approaching the theoretical limits of an x4 PCIe 2.0 slot

and might perform better in an x8 PCIe 2.0 slot.

7.5.3 Cleaning up the boot sequence

One of the most overlooked steps in completing a hardware setup is deciding from what you

are going to boot. The x3690 X5 server might have one or more ServeRAID controllers for

internal drives or perhaps another ServeRAID adapter for external drives. You might also use

one or more Fibre Channel host bus adapters (HBAs) to access a SAN and you might have

Preboot eXecution Environment (PXE) or iSCSI defined to boot to an OS over the network.

By default, your server and the installed options came with the ability to boot from any of

these sources besides USB storage devices. On every boot, the server recognizes each of

these boot choices, determines if bootable media is attached, and adds the optional ROM

support to the boot ROM to determine the correct device from which to boot. Checking all of

these boot choices adds time to the boot process.

To minimize this loss of time, you can disable the boot options for adapters that you know you

are never going to boot from. The following sections describe the common methods of

disabling boot options.

Legacy only mode

When the server is instructed to boot to Legacy Only mode, the best way to disable unwanted

boot sequences is to disable them in F1-Setup by selecting System Settings  Device and

I/O Ports  Enable / Disable Legacy Option ROM(s). Figure 7-19 on page 323 shows the

available options. You need to know the specific PCIe slots that are used for each adapter so

that you will know which slot to leave enabled.

Chapter 7. IBM System x3690 X5 323

Figure 7-19 Legacy Option ROM states

When booting from SAN with multiple paths for redundancy, you need to enable the legacy

option ROM for both HBAs.

The default UEFI mode

On the x3690 X5, you can sequence the order in which the UEFI will search the various

attached devices to locate a boot device. You can shorten the time that it takes to perform the

search by moving the adapter that contains the boot device to the top of the list.

In UEFI mode, PXE boot can be disabled for the onboard network interface card (NIC) ports

through F1-Setup by selecting System Settings  Network  PXE Configuration and then

by selecting the port from which you want to disable PXE boot. Figure 7-20 on page 324

shows the panel that you use to disable PXE boot on one of the two onboard network ports.

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Figure 7-20 Disabling PXE boot of the onboard network ports

Other PCI adapters can have their boot option ROM disabled from within their configuration

panels. To access individual adapter configuration panels from F1-Setup, select System

Settings  Adapters and UEFI Drivers. Figure 7-21 shows the available selections on this

panel.

Figure 7-21 Accessing adapter-specific configuration information