1U servers: Features and capabilities introduction

Internal 1U server characteristics

Processor support. Among the various features of 1U servers, processorsupport is often the first consideration. Today's 1U servers can routinely support one or two multicore CPUs, such as Intel's Xeon 5500 or Xeon 5600 families. Servers based on AMD processors generally use products in the Opteron 4100 or Opteron 6100 families. The Fujitsu Primergy RX200 S6 1U server (see Table 1) uses one or two Xeon 5600 family processors, while Dell Inc.’s PowerEdge R415 1U server uses one or two Opteron 4100 family processors.

Within each family, there are multiple models to choose from; each of which accommodates a unique mix of clock speeds, cores and cache sizes. Current processors incorporate six or eight cores. When you multiply this times the number of processors in the chassis and then optimize the instruction handling (using technologies such as Intel's Hyper-Threading Technology), each 1U server can deliver an astonishing amount of computing power. Since processor cores and computing cycles can be allocated by a hypervisor, servers can host numerous VMs. You can also choose a processor choice when you purchase the server or, alternatively, upgrade later. Just remember that in many cases, processors must be matched so that the same model, speed and manufacturing step (revision or version) is used.

Memory support. The second most important internal consideration is a server's memory support. Since virtual machines often run out of memory (or RAM) resources before they exhaust available processor cycles, organizations with virtual servers may place greater importance on memory than on processors. Today's 1U servers can support an enormous amount of RAM. Super Micro Computer Inc.’s 1026T-6RFT+ 1U server, for example, handles anywhere from 2 GB to 192 GB of memory in 18 dual In-line memory module (DIMM) slots (see Table 1). The Dell PowerEdge R415 1U server supports up to 128 GB of memory in eight DIMM slots.

Note that such large volumes of memory typically assume the use of registered (buffered) DIMMs. It is also possible to select unbuffered DIMMs, but the total amount of supported memory will be much lower -- perhaps one-half to one-third the registered amount. Also remember that memory is often installed per processor, so a 1U server with two processors and 12 DIMM slots will support six DIMM slots per processor. Virtually all memory used on 1U servers will be double data rate three (DDR3), which is the fastest memory type available to keep pace with current processor bus (front-side bus) speeds.

Other memory features are worth considering. Error-correcting code (ECC) memory is standard and can correct single-bit errors and detect double-bit errors in memory. A server administrator can use non-ECC memory, but forgoing the ability to detect and correct memory problems can expose key workloads to failure. Mission-critical 1U servers may benefit from single-device data correction (SDDC) memory, which extends the ECC paradigm to check and correct memory chip-level faults.

Hot-spare memory support serves the same function as that of disk hot spares. Extra memory modules, for example, are installed but not used. If a memory device fails, a hot spare can take over until the failed module is replaced. Memory mirroring is similar to RAID 0 (disk mirroring). Data is duplicated into two distinct areas of memory and compared. If an uncorrectable fault is detected in one memory area, the system continues running with data from the mirrored memory.

Drive support. Drive support is another hallmark of 1U servers, and today's crop of products can support numerous small form factor (usually 2.5-inch), SATA (serial ATA) and SAS (serial-attached SCSI) disks, along with an optical drive, such as a low-profile CD-ROM or DVD-ROM for loading software. It's critical to consider how a server will be deployed and the amount of local storage that a unit requires. If a server runs workloads from local storage, choose drives that provide the capacity and performance needed.

SAS, for example, offers reduced capacity and higher performance, which is ideal for general applications. SATA provides higher capacity and lower performance which may be a better fit for file and print servers. Products such as the HP ProLiant DL360 G7 and the Dell PowerEdge R415 1U servers can support solid-state (SSD) drives. While these drives are most costly, they also offer the fastest speed for databases and other storage-sensitive workloads such as databases or Exchange Server 2010 (see Table 1). The number of available bays depends on the server model and options, and some 1U servers do not ship with hard drives installed by default, so check a unit's configuration before ordering. Servers intended for shared-storage operation may not require local hard drives.

When admins use local hard drives, they should consider the availability of RAID for data protection. Modern 1U servers support fundamental hardware RAID modes such as RAID 0, RAID 1, RAID 5 and RAID 6. Additional modes including RAID 10, RAID 50, and RAID 60 may also be available. If a native disk controller on a server's motherboard does not support RAID, a separate RAID controller (and backup battery) can be added to one of the server's internal expansion slots.

Expansion slots. Servers in the 1U category also offer limited expansion capacity through one or more slots. These slots are typically available from riser cards located on the motherboard and can accommodate a range of enhancements such as RAID controllers, additional network adapters, storage area network (SAN) adapters such as a Fibre Channel host-bus adapters and so on. It's important to distinguish between PCIe (PCI Express) and PCI-X (PCI-eXtended) expansion slots -- the card types are not interchangeable.

The Super Micro 1026T-6RFT+ 1U server, for example, supports a low-profile PCIe x4 (four-channel) card, along with two PCIe x8 (eight-channel) cards. By comparison, the HP ProLiant DL360 G7 handles one PCIe x8 and one PCIe x16 card but if one changes the riser cards, this HP 1U model can support PCIe or PCI-X cards . The goal is to ensure that any upgrade cards for the server are compatible with the available space and number of channels available for a given slot. Otherwise the card won't fit in the server.

External 1U server characteristics

Power. Every server requires power provided through a standard alternating current (AC) cable suitable for the outlet voltage and style for your specific region of the world. Although power may seem like an obvious consideration, it’s particularly important to evaluate the need for resilient power features.

Super Micro ’s 1026T-6RFT+ 1U server (see Table 1) provides redundant, hot-swappable 700 watt (W) power modules – each with independent AC connections on the rear chassis. Other servers such as HP’s ProLiant DL360 G7 include a single 460 W power supply by default and offer the option to include a second redundant supply or use larger 750 W supplies. When multiple CPUs, large amounts of RAM, extensive drive installation, and numerous expansion cards are fitted to the server, the server unit needs larger power supplies.

This redundancy provides several potential benefits. A server will continue to run if either single power supply should fail. In addition, a server can be powered by two separate AC utility sources to guard against one utility fault. More commonly, a server can be powered by two independent uninterruptable power supply (UPS) systems. Budget-conscious organizations may prefer to power one supply directly from utility power and attach a UPS to the second supply. This eliminates the need for a second alternating current utility source and a second UPS.

Network connectivity. There are an increasing number of network connectivity options to consider. LAN ports are a crucial aspect of modern servers, so select a model that provides the connectivity that’s appropriate for a server’s load. A simple commodity server, for example, may supply only a single 1 Gigabit Ethernet (GbE) port, but more advanced servers often provide multiple 1 GbE LAN ports.

If you plan to deploy server virtualization and host multiple virtual machines on a physical box, a server with multiple ports is key. When high-end network connectivity is required (perhaps for servers intended to handle streaming media or heavy user workloads), consider a 1U server with one or two 10 GbE ports. As an example, the Super Micro 1026T-6RFT+ 1U server provides two 1 GbE and two 10 GbE ports on the same unit (see Table 1).

System manageability is an increasingly important issue for all types of servers, and the Intelligent Platform Management Interface (IPMI) is core to server management. Servers that support IPMI include a dedicated low-bandwidth local area network port that can send Simple Network Management Protocol alert messages (and other control communication) over the network. Administrators can also use IPMI traffic to check server status, hardware logs or perform other management tasks. A traditional serial (RS-232) port may also be included, but given the prevalence of network-based communication, it is rarely used.

User interface ports. The server also provides an assortment of user interface ports for the keyboard, video, mouse (KVM), along with numerous USB ports. In many cases, servers can be managed directly by connecting user-interface ports to a centralized KVM switch which is then directed to a single keyboard, video display and mouse at an administrator’s console nearby. A popular alternative is to use KVM-over-LAN or KVM-over-IP technology to access the server through a remote administrator console – perhaps located on a LAN in a nearby office or miles away across a WAN. USB ports can provide handy access for USB-based keyboards or mice (rather than traditional PS/2 port versions), external drives (for loading software), dongles for software package authentication and so on.

Controls and indicators. Many IT personnel pay little attention to the controls and indicators along a 1U server’s front panel. They may assume that diagnostics or system management tools provide the status and troubleshooting information needed, but one shouldn’t underestimate the ability to assess a server’s status at a glance.

Front-panel indicators -- such as system power, hard-drive activity, high- and low-speed network activity, and a series of alarms for temperature, power, and fan failures -- can confirm diagnostics or provide an early warning of potential problems without the hassle of formal diagnostics. Some servers provide a series of indicators, while other systems -- such as the HP ProLiant DL360 G7 - -provides a single "health" indicator through a series of blinks to report basic problems (see Table 1).

Indicators on a server’s individual drive bays can display the activity on individual disks or point to physical disk problems that guide a technician toward replacement. Also consider the availability of drive bays. Almost all current 1U servers provide hot-swappable hard drive bays. For example, the Super Micro 1026T-6RFT+ 1U server (see Table 1) provides eight hot-swappable bays for 2.5-inch form-factor SAS and SATA drives. By comparison, the HP ProLiant DL360 G7 provides four hot-swappable bays by default, with an option for four additional drives.

Each drive is mounted on a carrier to enable easy insertion and removal. Unlike common computers that connect drives to the system board with cables, 1U servers provide a fixed backplane that interfaces with the drive within its carrier once a drive is locked into the server chassis.

Note that servers intended for a shared-storage environment (such as server virtualization) may use few (if any) hard drives and, instead, boot from a network share and loading virtual machines from a SAN into server memory. A server can be configured for a Fibre Channel SAN by adding a Fibre Channel interface card to an internal expansion slot (covered below). If you plan to use a server with an Ethernet-based SAN (such as iSCSI), it can be interfaced from one of the server’s LAN ports (as discussed previously).

Manageability features for 1U servers

Even small and medium-sized data centers, servers have proliferated, so the ability to manage all that hardware is sometimes more important than installation or setup concerns. When considering a 1U server acquisition, planners should also look at the system’s manageability features. In general, a server can include hardware-based management features and software-based management tools.

Hardware-based management features. These features offer various bare-metal monitoring capabilities that can report faults regardless of the host operating system or server status. IPMI capability supports server monitoring and management between the system and IPMI-compatible management software with a low-bandwidth network link. IPMI works even when the server is off (just connected to power). For example, the Super Micro 1026T-6RFT+ and the Dell PowerEdge R415 1U servers (see Table 1) both provide IPMI 2.0 management. HP’s iLO (Integrated Lights-Out) approach offers similar hardware-level control through a dedicated network port. Dell incorporates a DRAC (Dell Remote Access Controller) such as its iDRAC6 into a server expansion slot to support power management, media access, and Web-based remote control capabilities.

Servers that support KVM-over-LAN (or KVM-over-IP) allow remote administrators to take direct control of a server from anywhere across the network as thouhgh they are accessing the keyboard, video, and mouse of the server itself. Other hardware-based features include onboard voltage monitors, chassis and CPU temperature sensors, fan monitoring and speed control. Server buyers can also find systems with virus protection and BIOS recovery built directly into the firmware.

Software-based management tools. These tools allow administrators to monitor and control servers from almost any location. Each 1U server includes its own management tool. For example, the HP ProLiant DL360 G7 includes Insight Control with iLO Advanced (iLO 3) allowing new server deployment, health management, remote control and power optimization (see Table 1). The Dell PowerEdge R415 1U server includes Dell OpenManage software with Dell Management Console. The Fujitsu Primergy RX200 S6 1U server includes ServerView Suite, which manages server installation, operation, RAID, updates, power and agents.

But software tools require extra consideration. Unlike hardware-based features which are often standardized architectures such as the BMC (baseboard management controller) built into computer chipsets, software tools are typically unique to specific server families or vendors. As a consequence, it's easy for software tools to proliferate in mixed-server environments without a heterogeneous management framework to manage everything collectively. Consider the number of tools -- and the learning curves for IT staff required to master them -- for new 1U servers. ServerView software with Fujitsu's Primergy RX200 S6 1U server can integrate with Microsoft SMS (Systems Management Server), MOM (Microsoft Operations Manager), SCOM (System Center Operations Manager), SCCM (System Center Configuration Manager) and Symantec/Altiris management software.  

A summary of 1U servers

Today, there are countless servers to choose from. Table 1 summarizes the most basic features of several major 1U server offerings. These servers are the meat and potatoes of modern enterprise computing, providing ample computing power in small, cost-effective rackmount packages.
Table 1 illustrates a cross-section of representative products as a starting point for your evaluation process. Also remember that the specifications below may vary depending on the particular vendor, system and options selected.

Table 1: Common 1U server specifications

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