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How to Choose the Right Server?
Continued from page: 2
Thursday, August 16, 2007
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.
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| 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.
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| 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 Page(s) 1 2 3
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