Installation guide
The Dell PowerEdge 6850 server is capable of running in several dierent modes, due to the EM64T processor. There two major
modes: IA32e mode and Legacy mode. IA32e mode is automacally invoked when a 64-bit OS is booted. Legacy mode is
automacally invoked when either a 32-bit OS or 16-bit OS is booted.
IA32e mode is based on the exisng IA32 mode, with 64-bit extensions. Under IA32e mode, two dierent sub-modes exist: 64-bit
mode and Compability mode. Both modes require that a 64-bit OS is booted, such as Windows Server 2003 64-bit for EM64T. 64-
bit mode takes advantage of the full register width. Up to 1 TB of memory is addressable, without the need for AWE memory. Com-
pability mode is automacally invoked for 32-bit applicaons, on a per code segment basis. This means that if you boot
the Dell PowerEdge 6850 server with Microso Windows Server 2003 64-bit EM64T version of the OS, you can run a mix of 32-bit
and 64-bit applicaons without compromising performance. Of course, applicaons that run in 32-bit mode sll access memory
above 4 GB with the AWE model, but the rst 4 GB is available without any OS overhead, which is an improvement over the standard
32-bit model.
Legacy mode is essenally the same as the exisng IA32 model. It contains three submodes: Protected mode, Virtual-8986 mode,
and Real mode. Real mode and Virtual-8986 mode are both used for 16-bit applicaons, and are used rarely. Under Legacy mode, the
most commonly used sub-mode will be Protected mode. It is automacally invoked when a 32-bit applicaon runs on a 32-bit OS.
With Protected mode, you can run a 32-bit OS, such as Windows Server 2003 with no negave performance impact. This is the mode
used in the RAC installaon example used in this paper. In Protected mode, memory access uses the 32-bit AWE model, with
behavior unchanged from previous Dell PowerEdge servers.
Impact of the Dell PowerEdge 6850 on RAC Implementaons
One of the main movaons in moving to Real Applicaon Clusters is to implement a High Availability infrastructure. Therefore, it
makes sense that an HA infrastructure should be composed of high quality components, with built-in internal redundancy and
reliability. The PowerEdge 6850 oers the highest level of RAS features available, and will make the ideal building block for a High
Availability RAC infrastructure. RAC is oen implemented to “scale out” for performance increases, as opposed to “scaling up”. With
the PowerEdge 6850, companies have the ability to scale up and scale out at the same me. As a RAC node, a single 6850 will
support large numbers of users and large workloads, due to the 4 processors and up to 64 GB of RAM. With up to eight nodes
supported in RAC conguraons, the PowerEdge 6850 is capable of supporng any Mission-Crical Enterprise workload with
outstanding performance.
The Dell PowerEdge 6850 Server with the Intel EM64T processor has the advantage of working equally well in 32-bit mode and 64-bit
mode. As Microso Windows 2003 Server for EM64T and 64-bit Oracle RAC for EM64T become available, the 6850 server will oer
the perfect route to transion to 64-bit RAC. In addion, the price/performance rao is parcularly aracve for a 64-bit server,
which is all the more important when mulplied by mulple RAC nodes.