the medium is considerably less expensive than disk or flash storage.
Part of the reason is that, unlike disks,
one tape machine can accommodate
an unlimited number of tape drives
or cartridges. An analysis conducted
by BackupWorks.com indicates that
equivalent levels of backup for tape versus disk results in about 4x cost savings
for devices.
There are other cost benefits as
well. These include a more than 2x
savings in operational costs, and upward of 10x savings in total power and
cooling costs. Today, a robotic tape
library can contain upward of 278 petabytes of data; the same data stored
on CDs would require almost 400 million discs.
Tape also delivers efficiency advantages. All devices, when they write bits
to storage, produce an “unrecoverable
bit error,” which occurs because the device writes a “ 1” instead of a “0” or vice
versa. Error-correction methods do not
make the problem completely go away.
The result for a commonly used tape
format such as an LT0-7/8 is a bit error
rate of 1:1018, which is approximately
one error for every 1. 25 exabytes (EB).
Other enterprise-class and consumer
drives perform at an error rate of about
1:1016, which translates to an error every 125 terabytes (TB). Although error-correction codes for storage technologies have improved over the years, tape
is about 100 times more accurate than
the best hard drives, and about 10
times better than the latest solid-state
devices (SSDs).
“The challenge with any storage technology is to reduce error
codes,” Heckel says. In a practical
sense, this means that tape systems
are more dependable than other
technology solutions. The greater
the unrecoverable bit error rate, the
greater the risk of loss of data, along
with other errors and problems,
including a system seeing two bad
drives simultaneously.
Yet, there’s still another consideration. Modern tape cartridges fail at
a rate about five orders of magnitude
less frequently than hard drives—and
tapes in storage require no moving or
mechanical device.
Finally, tape offers the added ap-
peal of creating an air-gapped environ-
ment when they are not in use. This
makes a tape library highly secure, as
long as it is kept physically protected.
Beyond Tape
Tape is not ideal for every situation.
Recovery from a tape backup can be
slow and somewhat cumbersome.
Finding specific files can prove vexing. If incorrectly stored, tapes can
succumb to environmental damage or
become demagnetized.
There’s also a bigger problem with
all current storage technologies. A typical hard drive will operate only about
three to five years before failing. Portable disk storage technologies such
as CDs and DVDs generally hold data
for 10 to 25 years, while flash storage—which includes drives, cards,
and SSDs—degrades with use, rather
than with age. This means that the
more a user writes and rewrites to the
device, essentially using it for its intended purpose, the greater the risk of
failure. Future improvements in hard
drives or flash technology are likely to
produce only marginal performance
gains, Heckel points out. However,
tape, stored under ideal conditions,
can last 30 to 50 years—and perhaps
even longer. Although none of these
technologies can compare to the lifes-pan of paper stored under ideal conditions (about 500 years), tape emerges as
a clear winner.
Yet there’s still another long-term
challenge: many existing storage technologies are butting up against physical and logical limits. It is increasingly difficult to add speed and capacity
through more heads, platters, or microchips. A handful of technologies
may help boost the power and scale
of hard drives, for example. These include heat-assisted magnetic recording (HAMR) and microwave-assisted
magnetic recording (MAMR). Both of
There are a number
of technical and
practical reasons
why tape has refused
to fade into history.
ACM
Member
News
PURSUING MULTI-PARTY
COMPUTATION
Tal Rabin, a
Distinguished
Research Staff
Member and
manager of
Cryptographic
Research at
Yorktown, NY, was born in
Massachusetts and grew up in
Jerusalem, Israel.
Rabin earned bachelor of
science, master of science, and
doctorate of science degrees
from the Hebrew University
of Jerusalem, all in computer
science. After obtaining
her Ph.D., Rabin served as
a postdoctoral fellow at the
Massachusetts Institute of
Technology for several years,
before joining IBM’s T. J. Watson
cryptography group.
Her research interests are in
various areas of cryptography,
with a primary focus on multi-
party computation, a way for
two or more parties to together
compute a function over their
inputs, while keeping the
individual inputs private.
Rabin is currently engaged is
designing a distributed protocol
that would enable people to
submit a sexual harassment
complaint, which would then
identify other potential victims
of that specific harasser. Rabin
explains that victims might be
more likely to move forward
with such a complaint if they
knew a group of people would
also be involved, so they would
not have to proceed alone.
“This is the beginning
of the road for having actual
applied multiparty computation
algorithms,” Rabin says, adding
that the next few years will be
exciting as these applications
come to fruition.
Rabin is also interested in
helping women advance in
computer science by getting
more women involved at the
undergraduate and graduate
levels, as well as in the
workplace. She acknowledges
that she does not have the
answers as to how this should be
done, but she hopes it will be a
community effort.
—John Delaney