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Common Problems with
Errors in Data Transmissions between Nodes
Unexplained Component Lockup
5. Hard Drive Crashes
6. Corruption or Loss of Data in CMOS and Other EPROM Chips
7. System Devices Behave Erratically when too many are turned on
Frequently Aborted Modern Transfer
10. Disc Drive Write Errors
are sensitive to their power environment. Anyone who has ever had a
computer toasted by a lightning strike or who has lost a morningís work
to a sudden blackout knows that all too well. But even with the
increased awareness of the need to protect computers from power
problems, many people still believe their vulnerability is limited to
the occasional storm or utility outage. There are two unfortunate
realities of the electronic age; the utility companies simply cannot
provide the clean, consistent power demand by sensitive electronics, and
you are responsible for the health and safe operation of your equipment.
In fact, studies suggest that the
electrical environment in which most computers operate is a far
"dirtier" place than we once realized. Final data from massive five-year
survey of power quality in North America conducted by National Power
Laboratory indicate that the average computer site is subject to 289
disruptive or destructive power disturbances per year. Moreover, the
most noticeable types of problems-blackouts and lightning
strikes-account for less than 12% of these events. Most are under- and
over-voltage conditions and electromagnetic interference-disruptions
that are nearly impossible to detect with the naked eye. A more recent
study by IBM has showed that a typical computer is subject to more than
120 power problems per month. The effect of the power problems range
from the subtle-Keyboard lockups, hardware degradation-to the dramatic
data loss or burnt motherboards.
So how do you know if electrical glitches
are disrupting or damaging your computer, short of investing a fortune
in power monitoring equipment? Here are ten tell-tale signs of power
trouble. While no single symptom is conclusive evidence of flaky power,
if your computer suffers two or three symptoms regularly, you should
probably look into an Uninterruptible Power System (UPS) or some other
power protection device.
Like blackouts and lightning strikes, this
is one sign that most people recognize as being power related. Flickering lights usually are a sign that your facility is experiencing
split second outages or voltage sags. Unfortunately, there is often a
tendency to dismiss these flickers as inconsequential; after all, they
are over with literally in the blink of an eye.
|But a computer
functions in a world where milliseconds count. While it may take an
outage of hundreds of milliseconds is sufficient to crash a network, if
your workstation is in the same office as the file server, you may
notice a tendency for the server to lock up after the lights flicker. If
your workstation is remote, however, you may never make the connection.
Workstations or non-critical may be fine with level 3 UPS. It is
recommended for servers and other critical equipment to use a level 9
UPS and a minimum of level 5 UPS.
Need help with your selection?
While this is one of the most common
problems LANs face, few network technicians recognize that power
problems may be the cause. Actually, two different kinds of power
aberrations can interfere with internode communications: ground loops
and electromagnetic interference (EMI).
|Ground loops can
occur between any two devices linked by a data cable, especially if the
devices are a considerable distance apart. When a significant voltage
difference develops between the two devices, the difference will "equalize" as an
impulse traveling on the cable. The result can be a scrambling of the
data carried on the cable; if the voltage potential is large enough, it
can even damage I/O cards.
EMI consists of electrical impulses
generated by noisy devices such as radio transmitters, fluorescent
lights, and even computer power supplies. These impulses travel through
the air, and a data cable can pick them up in the same way that an
antenna picks up broadcast signals. These conducted EMI impulses create
noise on the data cable, interfering with communication between
workstations, servers, and other peripherals.
Where possible, keep voltage differential from developing by plugging
all devices into a single grounding point, such as a Level 5 or Level 9
UPS. Use data line surge suppressors to prevent impulses from reaching
the computer. Run longer data cables through shielded, grounded metallic
conduit to prevent EMI from reaching the cable. Keep cable runs away
from noise generators-especially fluorescent lights.
with your selection?
Another common sign of power problems is
the tendency of servers or workstations to freeze. While many factors
can cause this sort of lockup, random system crashes are often a sign of
low voltage sags or subcycle power failures have sapped your logic
circuits of the voltage they need to operate properly. NPL and Bell Labs
power quality data show that voltage sags are the most common type of
operate on very low voltages: typically just 5 volts DC. Manufacturersí
tolerances for logic voltage are fairly tight; when voltage drops below
4.75 volts, RAM errors start to increase. If low-voltage sags or subcycle outages starve the computerís power supply, it may be unable to
maintain logic voltage, and the system crashes.
Ironically, certain Level 3 UPS's can also
cause this kind of logic voltage drop. While these devices may advertise
a fast transfer time in the event of a power outage, they are often
unable to provide full power for one or two cycles after the transfer.
In laboratory tests, computer logic voltage has been measured to drop as
low as 3.5 volts when powered by some inexpensive
Level 3 protections.
Use a Level 9 UPS which have no transfer time when powering your
computer to battery or use a quality level 5 UPS that will allow and
compensate for sags with a buck-boost internal transformer.
help with your selection?
When an I/O card, mother-board, power
supply, or other vital component suddenly fails for no apparent reason,
the failure is often blamed on manufacturing defect. In reality, the
quality control and burn programs of most reputable manufacturers make
built-in defects a rarity. The real cause is more likely to be latent
chip damage caused by a high voltage spike, line noise or harmonic
spikes, line noise and harmonic distortion do not always cause immediate
component failure. Often, the delicate conductive traces in a microchip
can simply be weakened by high voltage or heat dissipation, only to fail
weeks or months later, when the event the event that hastened the chipís
demise has faded from memory. Unless such component failures are
frequent, the network technician may never suspect the true cause of the
You say youíve protected you server with a
surge protector, and you are still getting component failure? Surge
protectors may protect against spikes, but does nothing for line noise
and harmonic distortion. It is possible that the surge device itself has
become the victim of repeated lightning strikes-especially if it is one
of the cheap hardware-store variety. Or spikes could be seeking into
your system via other routes, such as data cables or modem connectors.
Be sure that all network devices are protected by high-quality,
multi-stage surge suppressors, which carry a UL 1449 rating. Many level
3,5,and 9 protection carry this rating.
to find the appropriate solution for your application. See to it that
data cables and modern lines are also protected by surge suppressors.
While this nightmare is less frequent than
it used to be, hard drives still crash, and power problems can be to
Sudden power loss can be especially
dangerous to hard drives; if power fails during a read/write operation,
the heads can drop precipitously onto the disc, damaging the delicate
magnetic medium and creating bad sectors. If this damage occurs in the
wrong place, disk boot failures may result.
Solution: Use a quality UPS
system Level 3, 5 or 9, to provide enough backup power to allow you to
do an orderly shutdown of the system. Need help with your selection?
Many computer users have experienced the
horror of turning on their computer and finding that itís suffering from
amnesia; it no longer remembers how many drives it has, what kind of
monitor itís supporting, or how much memory is on its mother-board.
Again, bad power may be the culprit.
|With the arrival
of 386,486 and Pentium systems, vital system configuration data is
stored in ROM. High-voltage impulses can scramble the data on these
chips, forcing the user to do a system setup from scratch. CMOS chips
can also fall prey to electronic discharge (ESD) - that nasty, high-voltage
shock you sometimes get when you touch a metal object on a dry day. ESD
discharges can be several thousand volts in amplitude, enough to cause
you pain and to wipe a ROM chip clean.
Protect Equipment with high-quality surge suppressors. Use various
devices on the market (grounding wrist straps, touch-pads, anti-static
sprays, etc.) to reduce the risk of ESD near your computer. Need help
with your selection?
If your network begins to behave strangely
as more and more workstations are powered up, your problem could be
harmonics, which show up on oscilloscopes as current or voltage
distortions. Ironically, computers themselves are one of the biggest
sources of harmonics, because their power supplies draw current in big,
isolated gulps instead of nice smooth sine waves. If many of your
network devices are powered from the same circuit, the harmonic content
of that circuit can build as the devices are turned on. The result: the
more workstations operating, the flakier they behave.
Install a FERRUPS UPS or power conditioners, which feature a ferroresonant transformer. This special type of transformer is extremely
effective at filtering harmonics from the input line. A ferroresonant-based
device will also keep harmonics generated by the workstation from
affecting other computers on the same circuit. A level 9 UPS will also
provide protection against harmonics. Need help with your selection?
Power problems can cause modem
uploads/downloads to abort or cause a high rate of block messages. The
situation can arise when high-frequency spikes or impulses traveling on
the power line couple into phone lines, which are almost never protected
by any kind of shielding. These signals are then interpreted by the
receiving modem as bad blocks.
Surge suppressors and many UPS systems are now available that include
phone-line jacks. These devices can stop many of the impulses that
travel on any phone-lines. You simply plug the modem line into one jack,
and run another line from the second jack to the wall connection. Give
one of these devices a try if aborted modem transfers are recurrent
problem. Be certain the device you select is designed with a single
grounding point for both the electrical and modem or data line
connections. Need help with your selection?
If your display flickers, wavers, or
dances, it could be a sign of larger power problems that may be
affecting your entire network. Voltage sags can make monitor displays
shrink. A wavering display could also be a sign of strong
electromagnetic fields neat the monitor. Either of these situations can
do more than just disrupt your screen; they can cause RAM errors,
scramble data, and contribute to component failure.
Use a level 5, level 9 UPS or FERRUPS , which feature voltage
regulation, to keep input power at a proper level. Keep EMI generator
(especially electrical motors) well away from network peripherals. Need
help with your selection?
Because your hard and floppy drives are
really the only moving parts in your network, they are especially
vulnerable to power aberrations. Weíve already looked at two reasons:
damage caused by sudden loss, and RAM errors attributable to low logic
One additional way bad power affect disk
drives is to interfere with the rotation speed of the disks themselves.
Proper drive access depends on the correct rotation rate; undervoltages
can cause the drive to try to read or write data in the wrong sector.
Lost or garbled data, or actual drive failure, can result.
Solution: Protect equipment
with voltage-regulating devices, such as a level 5 or 9 UPS. Need help
with your selection?
Is poor power quality causing all of your
network woes? Probably not. Any device as complex as a computer is
vulnerable to failure from many sources, and networking many deices
together only compounds this vulnerability.
But donít be too quick to discount the
threat of bad power. A National Power Laboratory survey of 1,200
computer systems showed that the number of service calls dropped an
average of 82% after the installation of a UPS.
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