How to Choose the Right Server?

Workgroup servers have undergone a tremendous change in recent times with a

lot of new technologies hitting the market. This has made it difficult for IT

decision makers to choose the right one for their organization. The demand for

servers is increasing in India by leaps and bounds, and as a result we are

seeing that apart from the hardware majors, a lot of assemblers are also leaving

the PC space and jumping into the server arena. This has led to a major

reduction in price of branded servers.

Today we are going through a phase where processor technologies are improving

continuously and as a result we can now get a powerful server in just a couple

of Lakhs. And it is so powerful that if you had bought it ten years back, it

would have been amongst the top 50 supercomputers in the world. Such servers

take up only 2 U of a server rack. This has all been made possible because of

the availability of multi-core processors. Today, if you buy a server with a

dual Xeon, you get either the power of eight or four Xeon processors, depending

on whether you bought a quad core or a dual core server. Such a server not only

gives you commendable results in number crunching operations but also help you

in consolidating your datacenter. For example, the new age processors with

multi-core technology provide you with Virtualization support. This means you

can dedicate a single core to a given virtualized OS (which is essentially a

Server) and host 7 different server OSes on a single 2 U of a dual Quad-core

server. We say 7 instead of 8, as we assume that one core would be used for the

host server running the virtualization application.

You might wonder that if one is going to host 7 full-fledged servers on a

single quad-core server then how much memory can it support to cope with the

load of all such virtualized servers running on top of it? Well, rest assured,

these servers are not only capable enough to take a huge amount of processing

load but can also support RAM of different capacities, starting from 8 GB to 64

GB. This is enough to host any kind of application, including resource hungry

virtualization setups.

Another happening segment related to servers is storage. This segment has

essentially two concepts which are gaining importance rapidly. The first is the

penetration of Serial Attached SCSI (SAS) hard-disk. Since long SCSI was the de

facto standard for Server Direct Attached Storage (DAS). But, due to certain

limitations such as the maximum number of disks per channel and total

throughout, SAS is taking its place today. You will read more about SAS and its

features, later in this article. The second concept that is gaining importance

is the use of Host Bus Adapter (HBA) cards. These are the cards that connect the

Host (computer) to storage over iSCSI, Fiber Channel, etc. Now let's discuss all

of the above points in detail.

How much RAM?



When choosing a hardware configuration, remember that each application has a

different requirement. For instance, if you plan to use your server as a Web

Server with a lot of static content (such as a Web portal) or as a file or

networked server, then the amount of RAM doesn't really matter much, assuming

you have at least 4 GB RAM. This has become standard nowadays. We came to this

conclusion after running our set of I/O, disk and Web benchmarks, on the same

server, with 4 GB and 8 GB RAM. In case of Web requests, the performance was the

same for both configurations, while in case of file server I/O, the performance

improved by 10% with higher RAM. That's hardly an increment worth spending for

extra RAM.

What matters the most in these cases are disk and network speed. Once again,

while testing the servers, we noticed that when you stress a server's disk

access performance over the network, then the first thing to get choked is your

Gigabit Ethernet card. This results in data transfer speeds of just below 1,000

Mbps. To rectify this, we joined two Ethernet cards while running network based

benchmarks. Such an arrangement gave us double the bandwidth. We've given a

detailed report on how we ran the benchmarks in the “how we tested' section. So

here's a tip: Before thinking of upgrading your processor or RAM for I/O

intensive applications, first try teaming the free LAN cards.

Some servers came with small from HDDs (Laptop HDDs), to save on space and power consumption

Which Hard Drive?



Another important parameter for I/O intensive networked servers is hard disk

performance. This is also critical for database servers. But to get optimum

performance, you require a very high capacity hard disk with maximum rpm and

throughput, and that too in large numbers. You can actually get better

performance out of five 10,000 rpm SATA HDDs than what you can get from two

15,000 rpm SAS drives. But it depends on how much you can spend and what's more

important for you. If redundancy is not important and you have three HDDs, then

you can connect all of them in RAID 0 (Stripping mode) and get some really

extraordinary performance.

Now, if redundancy is extremely important, which is the case with most users,

you can go for RAID 5 with more hard disks (let's say 6 instead of 3) so that

you can reduce the performance degradation while writing parity information, and

get performance which is equivalent to having two disks in RAID 0.

This time we got all the servers with hot swappable SMPS, the max number was 3

Specs for compute intensive servers



The two key things that matter in this are of course, RAM and CPU power.

Plan on going for lots of RAM and a high-speed CPU if you're putting the server

to heavy duty number crunching or memory and CPU intensive applications like

virtualization. Even if you don't have a high-speed CPU, make sure that the

vendor let's you upgrade to one later. Some vendors don't offer CPU upgrades in

their server configurations. The same logic also holds valid for servers which

are used for huge number crunching, for eg, for servers that will be a node of a

cluster for doing huge data processing. One very important point to note here is

the architecture that your application has been designed for. If it's designed

for Intel architecture, then don't expect excellent performance on an AMD

platform, and vice versa.

We came to this conclusion after doing a very interesting exercise. While

deciding benchmarks to be run on all servers for testing processor performance

we first thought of using HPL (High Performance Linpack) compiled on Intel

multi-core architecture. This benchmark was provided by Intel's Server division.

When we ran this benchmark on Intel servers, it gave us 27 GFlops on Dual Core

Xeons and 53 GFlops on Quad Core Xeons. But when we ran the same test on an AMD

Dual Core, we got only 4 GFlops. This was strange as the AMD machine was, till

that point, outperforming most of the other servers. We felt there was something

wrong. As a result, we approached AMD and asked them to compile and customize

HPL for their dual core architecture. However, they were not able to provide a

customized HPL on time. So, we decided to use a processor testing benchmark

which is more real life and generic. Read more about how we stressed the

processors of various servers in 'How we tested' section.

Hot swappable hard disks are today the most common redundancy feature of servers. All the servers which we received this time had feature	More RAM slots can either be used for redundancy by distributing RAM in smallest possible chunks, or it can be used for upgradability

Service and Support



While buying a server one important aspect that should never be neglected is

the kind of support and service provided by the vendor. Different vendors have

different schemes. Though most of them provide 3 years warranty, some provide

services within a specified locality, while yet others have a deeper

penetration. For eg, if your server is installed in a remote location, a vendor,

local to a particular area, might not have a service center there and may take

time to address your problem. However, the vendor of a branded server, available

globally, would be able to address your problem by the next working day. Some

vendors tie up with local, authorized service providers to cater to the needs of

people in remote areas, where they themselves don't have any existence. There

are also vendors who provide specific services for specific needs. You need to

pay for the desired service and they will make sure that your problem is

resolved within 4 hours from the time you called them. There are other vendors

who offer you 3 year warranty with 24x7 support. But if you plan to install your

server in major cities, you might as well consider local vendors who would have

branches at least in the major cities and would be more cost effective.

Manageability



 These days servers ship with embedded sensors in chassis and

motherboard, which can help you extract information using server agents and send

them to a centralized remote console. Monitoring the server's health and

well-being remotely is a key concern for all. Some of the servers we received

had Server Management port that enables you to monitor your server over the

network. The servers also included an Intel Deployment kit that has a graphical

interface and helps you configure your server easily. Also, the Intel System

Management software allows you to monitor disk space usage and has the option to

alert the administrator when updates for firmware and BIOS are required. Some

vendors also provide their own customized Server Management CD through which you

can monitor the performance and health of the server, get reports on regular

basis and install the desired OS.

Another important component of manageability is Out of Band management also

known as LOM (lights out management) which lets you remotely manage the server

irrespective of the status of server. Using this you can only configure the

settings before the OS boots, i.e. RAID, BIOS level configuration. Two popular

ways of Out of Band management include Console redirection and BMC (Baseboard

Management Controller) management card. The console redirection is done through

the serial port with mostly a modem attached to it, you can send keyboard input

and receive text output, no GUI output is supported. BMC lets you interact with

distributed management cards using IPMI (Intelligent Platform Management

Interface). BMC now comes integrated with most of the boards else you can also

add a separate BMC card.

Reliability and Fault Tolerance



Servers are critical for any establishment and hence their reliability is

crucial. Any kind of hardware failure not only causes data loss and server

downtime but also affects the business economy. To ensure that you avoid any

kind of hardware issues, it's always preferable to have redundancy features in

the server, which take care of data protection and will continue to run the

server, even if one component fails. RAID is always considered to be a vital

solution for servers. If a server is storing high-value user data it is

preferable that they use RAID 5 configuration, which can only be achieved with

minimum of 3 hard disks.

While RAID provides protection against single disk failure, you will need

your hard disk to be hot swappable to make sure that you can replace the faulty

drive without bringing your server down. So Hot Swappable HDD enables you to

replace the faulty drives with a new one while your systems are still running.

This also enables you to avoid any unnecessary downtime.

Fans are vital for any server; they help to keep the server cool, so as to

avoid any performance bottleneck. Every server is equipped with certain number

of fans which are required to keep the server cool and performing, but if one

fan goes for a toss then their might be a possibility that your server

performance will decrease as it generates more and more heat.

So a hot swappable fan will enable you to replace the faulty fan even while

the server is running. Another key requirement is to have a hot plug and

redundant power supply which make the server fault tolerant against the failure

of an SMPS or even it can take care of power failure in case of single phase

failure or power cable failure if configured properly.

There are a few other very critical aspects of reliability that must also be

kept in mind. These include a server's resistance to extreme temperatures,

humidity, and vibrations. If you're buying servers for locations across the

country, then you must ensure that the server can withstand these environmental

conditions in those areas.

We had contacted ERTL Lab, which is a govt-owned test lab for environmental

factors. However, we were not able to pursue it much due to shortage of time.

Nevertheless, it's always good to ask the vendor for some reports on how well

can it withstand environmental factors.

Hot swappable Fans are something which we saw for the first time. Two out of nine servers we received had this feature

Expandability



With the growing need of users and organization, one of the vital decisions

while buying a server would be the expandability. A server should have enough

options for expandability should the need arise in the future. As user needs are

growing, so is the data. So storage capacity is one of the most vital

expandability options. What is the maximum number of disks the server allows you

to add?

We have seen that a maximum of 8 drive slots are available in a server, while

some offer 6 drive slots and 4 is standard across others. An SAS (Serial

Attached SCSI) can accommodate up to 1600 plus devices in one channel compared

to SCSI which can accommodate only 32. SAS uses serial communication instead of

parallel method and hence is capable of providing higher speed data transfer. So

SAS is preferred over SCSI nowadays. As far as SATA is concerned it offers

lesser expansion in terms of number of disks. An external SCSI connector enables

you to connect external SCSI devices like tape drives without the need to open

the server cabinet for connecting it.

You also need to consider how many DIMM slots are supported by the server as

they help you to add additional RAM, so if your server supports 16 GB of RAM but

there are only 4 DIMM slots available that means you need to plug a 4 GB RAM in

each of the slot, which might be an expensive affair. So more the number of DIMM

slots, better it is. Also, PCI-X (64-bit) slots help you to add additional fiber

channels or RAID cards, which you might include as the need arises. Hence you

are also required to consider the number of free PCI-X slots available. RAM

upgrade capability of a server can go up to a maximum of 64 GB, while some offer

32 GB, 16 GB upgradeability was common across most of them. Any server providing

less than 16 GB of RAM upgrade option is not worth the deal, as more and more

applications are becoming memory hungry and sooner than later you will require

higher RAM support.

The maximum number of RAM slots we this time was 16 and came with an assembled server

Now with Quad Core already available in the market, processor upgradeability

is an option that must not be neglected. Almost all vendors offer processor

upgradeability, there are some who don't offer it as a field operation, even

though processor can be upgraded on the same socket.

HBAs (Host Bus Adapters) are one of the most sought options in servers.

Though not many vendors provide it as a default option, still it can be

additionally added and it helps you to add host system to other network and

storage devices. We have mainly looked into fiber optic HBA which acts as

gateway to external SAN, though there are other types as well like ATA, SAS/SATA,

eSATA etc.

Anindya Roy, Saurangshu Kanunjna, Swapnil Arora with help from Jasmine Desai,

Jayanta Ghosh, Vijay Chauhan