Entry Level/Workgroup Server Buying Guide
Buyers' Guide to Entry Level/Workgroup Server
- What is a server?
- Server hardware on the market
- Server technical specifications
- Warranty and support
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This buying guide provides a thorough overview of server hardware with a focus on CPU-based, entry-level/workgroup devices from Intel and AMD. While it is structured for first-time buyers with IT experience as well as for business managers, experienced server buyers will also benefit from the coverage of the latest technologies around which these products are built.A server is a networked computer, or an application on a networked computer, that is used to distribute information, programs or resources from a central point to other computers and resources on a network.
Server hardware is a basic component of business-quality IT infrastructure. Servers are dedicated, high-reliability computers that are generally used to support multi-user business applications (software).
These multi-user, business applications are often referred to as server software.
For example, an application such as the Oracle Database runs on a [hardware] server. The combination is referred to as a database server. Another example is Microsoft Exchange: running on server hardware this is referred to as an e-mail server.
Software server applications share one common attribute: they run specific functions on a network-accessed machine remote to the user, and serve the results up to the user across a network.
It's important to note that software server applications do not have to run on server hardware. However, the requirements of high-availability and high-reliability generally ensure that they do.
Serving up some history
Years ago most IT infrastructures were centred on the mainframe. These generally physically-massive machines provide multi-user access to operators. The machines themselves ran multi-user mainframe operating systems, with access to users provided through terminals (devices which provide screen and keyboard access generally via a direct connection to the mainframe).
While there were many advantages to mainframes - and many businesses still use them today - they had their drawbacks. The main problem was that they were expensive - the growing use of IT in organizations meant gaining adequate access to the mainframe computing resources was a challenge, despite their multi-user capabilities.
This issue led to the rise of the minicomputer. The minicomputer could do most of the functions of the mainframe, at a lower cost. They were still expensive; however, businesses could buy a number of minicomputers instead of - or in addition to - the mainframe infrastructure.
Minicomputers, like the mainframe, run multi-user operating systems and are accessed through terminals.
Client-side computing
Mainframes and minicomputers needed trained operators and programmers. Most of the applications written for these systems were specific to the business needs. The introduction of personal computers - particularly the IBM PC and Apple systems - saw the writing of business applications, which could be used by a wide range of users without programming skills.One of the keys to these applications was the spreadsheet. Managers, with no programming skills, could use these applications for ad hoc business modelling and reporting.
While PCs were expensive and unreliable when compared to the machines available today, they provided managers with dedicated access to computing resources. This led to the rapid adoption of PCs in business.
This proliferation of PCs drove the introduction of local area networks (LANs) across organizations. The need for business managers to share their files was the driving force. And it also allowed some costs to be centralised - printers, which were still expensive at the time, could be shared amongst many users.
The common configuration at the time was to have user files stored on centralised Intel-based server hardware, generally running Novell NetWare rather than on client PCs. Printers and tape backup hardware were attached to these centralised servers.
At first, this centralised, Intel-based server hardware was just a PC with extra memory. However, over time this hardware took on features that added to reliability.
Client-server to the fore
Very quickly PCs began to have more and more processing power, which led to the rise of client/server computing, the essence of most recent computing infrastructure, and has driven the market for server hardware.File serving - as described earlier - is perhaps the simplest form of client/server computing. An example of this is a user running a spreadsheet on their client machine, but with the file stored on a network server. In this example of client/server computing, the client does most of the computation while the server essentially provides disk access and the computing resources to move the data off the server's disk and onto the network.
Software application servers generally place the emphasis on the server carrying out most of the computation. For example, a client-side application may request some information from a database server. The database server will perform the calculations required and provide the results back to the client application. The client application can then manipulate and present the results to the user, using the computational power of the client system.
In the example of a Web server serving pages built around server-side scripting languages such as ASP or PHP, the server performs all the work, with only the client rendering the results. In pages that include client-side Java or JavaScript, the client will provide not only support presentation but also run the Java.
Another common configuration is a server running the Windows Server operating system and Windows Terminal Server. Application software runs on the server with access to the applications from the client made using Terminal Server software. The Terminal Server software transmits screen, keyboard and mouse information to the Terminal Server client software running on the client PCs. The server hardware is running the entire application for multiple users.
From the early days of Novell NetWare-based file servers to today's client/server oriented market, server hardware has really matured. Now, server hardware is predominantly designed to meet specific application needs.Nevertheless, three simple factors continue to differentiate a server from other computer systems:
- Performance: Essential to provide acceptable levels of service to multiple users, a server can include performance boosting features such as multiple CPUs, high-performance disk systems, and loads of RAM.
- Scalability: The flexibility to add CPUs, RAM, hard disk storage and more in order to cope with increased load or new applications.
- Reliability and redundancy: If a desktop machine fails, one user is affected. If a server fails, the whole company might be stopped. Components with high MTBF (mean time between failure) figures and redundant components for when they do fail can keep your business up and running
There are servers that are designed to be used for high-availability, heavy use data centres, servers designed for workgroups or small/medium business, servers designed to maximize the amount of computing power that can be housed in 19in computer racks, and even server clusters to deliver massive computational power.
Rack mounted servers: While pretty much all servers today can be mounted in 19in computer racks, 'rack mounted servers' are designed to use the minimum amount of space possible.
Generally one or two rack units high (there are 42 units in a full rack) they range in capabilities from medium to high performance computing. The thinner, one -rack unit systems (1.75in) usually have very limited space for disk drives and little room for expansion. Many organizations deploy these rack servers in the computer rooms where space is limited, or in co-location premises where space is paid for by the rack-unit. The premium paid for their small size is generally easily made up for the space and/or cost saving.
Blade servers: A Blade server is a computer system on a motherboard that contains one or many CPUs and memory.
The thin design allows more computing power to be packed into a smaller space than typical 1U rack servers. These servers are made up of a blade server chassis, into which server 'blades' are inserted. Usually these blades can be added and removed as required, while the system is still switched on. This makes them well suited to high-availability server systems. The complexity of connectivity and cabling is also reduced for these systems. A premium is paid for these capabilities.
Entry-level/workgroup servers: these are generally housed in what most users would recognize as 'server' boxes. They are not overly large; however; little premium is placed on their compact size. They can generally support significant internal expansion hardware including disk drives.
Large organisations will likely deploy most of these server types to provide their computing infrastructure. Rack and blade servers will be used in major office computer rooms, and co-location installations. Rack and entry-level workgroup servers will be used in remote or satellite offices.
Small and medium organizations will tend toward entry-level and workgroup servers and lower-end rack servers.
Server technical specifications
Vendors supply technical specifications with servers, much as they do with other IT hardware. These technical specifications provide the detail you need to determine if the server is the right model for your requirements.If you know what to look for in a PC, you are a long way to understanding what to look for in a server. The following overview of server components will help you align the technical specifications sheet with the overall function of the server.
CPU
The Central Processing Unit (CPU) is a microprocessor that performs most of the data processing. It is the main processor in the computer and often one of the more expensive components in a server. Servers can have one or more processors.Servers can have CPUs from a range of vendors. Intel, AMD, Sun Microsystems, Hewlett-Packard, IBM and Motorola all make server-specific CPUs. The primary provider of CPUs for entry-level and workgroup servers is Intel and AMD.
- Intel server CPUs: Pentium III Xeon, Xeon, Xeon MP, Itanium, Itanium2.
- AMD server CPUs: Athlon MP, Opteron.
One of the primary differences between CPUs used in PCs and those in servers is that servers have multiple CPUs, which provides improved performance and availability.
Memory
RAM (Random Access Memory) is a high-speed form of storage that gives the CPU quick access to data.The basic rule of thumb is, the faster the RAM - and the more of it - the faster the computer performs. Servers can generally accommodate significant amounts of specific RAM designed for speed and accuracy.
Most current Intel- or AMD-based servers will use DDR (Double Data Rate) SDRAM (Synchronous Dynamic Random Access Memory). Some current servers will use SDRAM.
RDRAM (Rambus Dynamic Random Access Memory) is an alternative memory technology designed to work with motherboards and CPUs that use an 800MHz Front Side Bus.
Memory may also be available in ECC (Error Correcting Code) format. The memory itself adds extra information to the data that it processes in order to ensure its correctness.
Based on the current state of the memory market, it is advisable to configure servers with at least 1GB of ECC DDR SDRAM. Your server software provider may recommend more.
Storage
Data is stored on hard disk drives. Hard disk drives in file servers are based on technology, which provides the fastest transfer of information while at the same time offering the best-of-breed data integrity.Servers are generally configured with multiple hard drives, deployed in such a way as to vastly decrease the chances of data loss due to hard disk failure. This also provides greater storage volumes.
If physical space is insufficient inside the server to support the number of hard disk drives required, external storage system may be used.
Hard Disk Drives: Commonly, hard disks in servers differentiate themselves by their interface connections, disk spin speeds, latency times and buffers. These four items all affect performance and price. The SCSI interface has been the most common in servers as it allows for far more data to be throughput than an IDE connection. (The relatively recent advent of the Serial ATA (SATA) interface provides for throughput comparable to SCSI drives at a lower cost.) Disk spin speeds refers to the rotation rate - or revolutions per second - of the disks within the drives.
Higher spin speeds improve performance. SCSI throughput is comparable to IDE throughput. The benefit of SCSI is parallelization. That is, as you add more disks, you scale better than linearly. This isn't the case with large IDE systems. SCSI disks are also designed with reliability in mind. For example, many IDE disks ship configured to *not* flush buffers even when instructed. Only a very small number of SCSI disks are configured by default in this way. Latency is how long you wait before you start receiving data (throughput is the rate at which you receive it, once you start receiving it). Lower latency results in better drive performance. Finally, the size of disk buffers is measured in megabytes and refers to a temporary storage area that assists the drive interface to process the data with integrity.
Hard drive interface speeds
- ATA100 (also ATA 6): 100MBps
- ATA133 (also ATA7): 133MBps
- Serial ATA (also Ultra ATA): 150MBps to 300MBps to be ratified shortly
- Ultra3 SCSI: 160MBps
- Ultra160 SCSI: 160MBps
- Ultra320 SCSI: 320MBps
RAID: RAID (Redundant Array of Independent Disks) allows multiple disks to be connected together as one virtual drive for performance, redundancy, or both. In most cases RAID is used to provide redundancy. This allows a hard disk to fail without loss of data or uptime. If a hot-swap disk drive is available, the RAID system can be configured to switch over to using the spare disk. If the disk drives are hot pluggable, the faulty disk can be replaced and configured to become the new hot-swappable drive. It is essential to check that the operating system you intend to run will support the RAID controller in the server you are going to buy.
In an entry-level/workgroup server, you may wish to consider mirrored (RAID), ATA or SCSI drives onto which the operating system and applications are installed.
For more information on RAID, see the table below.
Connectivity
Without connectivity a server is useless. Ethernet running at 10, 100 or 1000Mbps is the de facto local area networking standard. Most entry-level/workgroup servers will include 10/100Mbps Ethernet NICs (network interface cards). If you require Gigabit Ethernet or other networking technology you will probably have to specify that at purchase time, or buy the network cards separately.
Be sure to check that the NICs are supported by the operating system you intend to run.
You may wish to include redundant NICs in your server. This will allow the server to transparently reroute network traffic from a NIC in the server that has failed to another working NIC in the server, without having to stop users from working by shutting down the network to effect repairs. You will have to configure your server operating system and network to support this.
This is a RAIDRAID Level 0: This is the most basic model. Features: data striping, without fault tolerance, works on a normal hard drive, data is stored on consecutive sectors of the same disk. Uses a minimum of two disk drives and divides data into blocks that range from 512 bytes to several MBs, which are written alternately to the disks. When the system reaches the final drive in the array, it writes to the next available segment of Drive 1, and so forth. Striping the data distributes the I/O load evenly across all the drives. And since drives can be written to or read from simultaneously, performance increases noticeably. Well suited to applications such as video production and editing or image editing. RAID Level 1: Is disk mirroring and duplexing- everything written to Disk 1 is also written to Disk 2 and can be read from either disk. This provides instant backup but requires the highest number of disk drives and doesn't improve performance. Offering the best performance and fault tolerance in a multiuser system, RAID 1 is the easiest configuration to implement, and it works best for accounting, payroll, financial and high-availability data. RAID Level 2: Was developed for mainframes and supercomputers. It corrects data on the fly, but RAID 2 is prone to high error-checking and correcting ratios. RAID Level 3: Includes data striping, but it also assigns one drive to store parity information. This provides some fault tolerance and is especially useful in data-intensive or single-user environments for accessing long sequential records. RAID 3 doesn't overlap I/O, and it requires synchronised-spindle drives to prevent performance degradation with short records. RAID Level 4: Includes large stripes so that records can be read from any single drive. It's rarely used because it lacks support for multiple simultaneous write operations. RAID Level 5: Is similar to Level 0, but instead of dividing data into blocks, it stripes the bits of each byte across multiple disks. This byte-striping adds overhead, but if a drive fails, it can be replaced and the data reconstructed from parity and error-correcting codes. RAID 5 overlaps all read/write operations. It requires three to five disks for the array and is best suited to multiuser systems that don't need critical performance or that do few write operations. RAID Level 6: Is rarely implemented commercially. It extends RAID 5 using a second parity scheme distributed over different drives. It can sustain multiple simultaneous drive failures, but performance, especially for write operations, is poor, and the system requires an extremely complex controller. RAID Level 7: Includes a real-time embedded operating system as a controller and high-speed bus for caching. It gives fast I/O, but it's expensive. RAID Level 10 or 0 + 1: A combination of RAID Levels that utilises multiple RAID 1 (mirrored) sets into a single array. Data is striped across all mirrored sets. As a comparison to RAID 5 where lower cost and fault tolerance is important, RAID 0+1 utilises several drives to stripe data (increased performance) and then makes a copy of the striped drives to provide redundancy. Any disk can fail and no data is lost as long as the mirror of that disk is still operational. The mirrored disks eliminate the overhead and delay of parity. Offers high data transfer advantages of striped arrays and increased data accessibility. System performance during a drive rebuild is also better than that of parity based arrays, since data does not need to be regenerated from parity information, but is copied from the other mirrored drive. RAID level 0 + 5 or 50: A combination of RAID levels that utilises multiple RAID 5 sets striped in a single array. A single hard drive failure can occur in each of the RAID 5 sides without any loss of data on the entire array. If, however more than one disk is lost in any of the RAID 5 arrays all the data in the array is lost. As the number of hard drives increase in an array, so does the possibility of a single hard drive failure. Although there is an increased write performance, once a hard drive fails and reconstruction takes place, there is a noticeable decrease in performance, data/program access will be slower, and transfer speeds on the array will be effected. RAID Level 53: Is implemented as a Level 0 striped array, in which each segment is a RAID 3 array. It has the same redundancy and fault tolerance as RAID 3. This could be useful for IT systems needing a RAID 3 configuration with high data-transfer rates, but it's expensive and inefficient. |
However, this type of configuration has two drawbacks - cost and complexity. Often the cost for permanent uptime is far beyond the losses that would be incurred should the server fail.
The reliability of a server installation is a trade-off between the amount spent on building in redundancy versus the losses incurred financially and to reputation in the event of server 'downtime'.
Server vendors know this. Consequently they provide not only a range of hardware with varying levels of reliability, but also support services of varying responsiveness.
Most servers come with three years parts and labour warranty. Generally, this is a Monday to Friday, business hours, on-site warranty. In other words, they will come to your site to fix the problem by the end of the next business day.
Of course, this means that should your server fail at 9am on a Friday, the vendor is obliged to fix it by the end of business the following Monday. While most vendors will endeavour to do better, your server could be out of operation for 80 hours over the weekend.
Consequently server vendors will sell you guaranteed response times, generally four-hour or two-hour. These can also be purchased for business hours Monday to Friday or 24 hours a day, 7 days a week.
The support option you choose will be dictated by the redundancy level of the server(s) you have purchased, the cost of the support options, and the losses that may be incurred from downtime.
It is also possible to purchase warranty extensions for new hardware to extend the warranty beyond three years. Most vendors will sell you these warranty extensions both at the time of server purchase or prior to the three-year warranty expiring.
Selecting your server
Your choice and configuration of server will be guided by the numbers of simultaneous users and the choice of server applications.
Your software company should be able to tell you the recommended server configurations for their software. This should include configuration details such as how many CPUs it should have, the amount of memory needed, the expected storage requirements and the server OS supported.