Servers

It's imperative to buy the right server to get maximum performance from your IT infrastructure. This advice would prove handy before you buy

Friday, September 05, 2008

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Servers are the heart of any enterprise IT network. When buying a server you have to answer a lot of questions: which processor should it contain; which OS should it be loaded with; expandability options, etc. Just as you buy other IT equipment, for buying servers, start by identifying your real need. Remember as most server purchases are done in bulk, future upgradability should be paramount. You don't want to be in a situation where you bought servers a year back and for which latest upgrades are available, but you are constrained by its architecture to upgrade. For eg, a year back someone bought dual core servers, and now wants to upgrade the processors to Quad Core, but the motherboard doesn't support it. So, make sure you have the flexibility of upgrading the server before you decide to buy one.

With several new technologies coming out, rules of server buying have changed slightly. Earlier everyone would refer to benchmark results and buy servers accordingly, ie if a server scores well in a computation benchmark, they would buy it for database needs, and the same logic would apply if you need a web server or an application server. Now when you buy servers, you are most likely to deploy a third party virtualization solution and run database, mail, web server, etc on top of it. Since all servers support processor level virtualization, the question you need to ask yourself is how many cores are enough for the application you are planning to deploy. Here another important point is that at least one core will be used by the virtualization application you are planning to deploy. In recent projects that we have done a case study on, we saw that 25 to 30 servers can be easily consolidated over an 8 CPU dual core server with 64 GB RAM. Once you have determined the number of cores for your application, you should start looking at how well a server performs in other benchmarks and what are your other priorities, may be your company plans to go green and you need a server which consumes less power. Similarly, if you are a web hosting provider, you should look for servers that perform well in benchmarks such as Web bench. While the number of processors and cores is an important part of server buying, do not ignore other hardware specs.

What specs to go for?
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 network server, then the amount of RAM doesn't really matter much, assuming you have at least 4 GB RAM, which is the norm these days. However, if you are going to deploy a virtualization solution and run everything on top of it, chances are that the minimum RAM you would need is 32 GB. Here again make sure you have the option to upgrade it. If you are going for high-end servers, most vendors would allow a RAM upgrade from 512GB to 2TB.

The next important parameter is hard disk. 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 get from two 15,000 rpm SAS drives. But all 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 can connect all of them in RAID 0 (Stripping mode) and get some really extraordinary performance. But, 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 performance degradation while writing parity information, and get performance which is equivalent to having two disks in RAID 0.

Support
As most servers are used for mission critical tasks, it very important to be clear about the support from vendors and if possible have stringent SLAs. Vendors have different support schemes. Most of the vendors provide 3 years warranty while others provide services within a specified locality. A few well-established players would also provide support in remote areas. For remote deployments, vendors also tie up with local service providers to reduce the time taken in resolving issues. Some vendors also offer quicker service response times for extra money. For eg, one of the options is a guaranteed 4 hour resolution from the time you called them. Others even offer you a 3 year warranty with 24x7 support.

Expandability
When buying a new server make sure that you have enough options for expandability in future. Data in an enterprise always grows faster than predicted, so the storage capacity of a server is extremely crucial. Check what's the maximum number of disks the server allows you to add? Usually a maximum of 8 drive slots are available in a server, but some might offer only 6 drive slots or even 4. A 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 and hence is capable of providing high speed data transfer. So, SAS is preferred over SCSI nowadays. As far as SATA is concerned, it offers lesser expansion in terms of the number of disks that can be added. An external SCSI connector enables you to connect external SCSI devices like tape drives without the need to open the server cabinet for connection. Similarly, you should also 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 capacity of a server can go up to a maximum of 64 GB, but 32 GB and 16 GB are the common options. Any server providing less than 16 GB of RAM upgrade is not worth the deal, as more and more applications are becoming memory hungry and sooner than later you shall require a higher RAM support.

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