Just as the power crunch, which began in the server
industry, has become the future for storage, the approaches to
fixing the problem may also originate there, as well.
According to some experts, recent research on the server side
into methods to reduce the number of power conversions required to
get energy from a wall socket into a computer could drastically
reduce power consumption in both servers and storage if widely
adopted.
In many
datacentres, according to Don Beaty, an IT consultant with DLB
Associates and a member of the ASHRAE TC 9.9 committee, which
focuses on datacentre power and cooling issues, converting between
alternating current (AC, or wall power) and direct current (DC, or
battery power) takes multiple steps.
"From the utility source down to the server and then within the
server there are multiple conversions occurring, each of which
represents some
loss of energy," according to Beaty.
Bill Tschudi, principal investigator for the applications team
in the environmental energy technologies division at Lawrence
Berkeley National Lab (LBNL), said he has been working with server
vendors, as well as the U.S. Department of Energy (DoE) and the
Environmental Protection Agency (EPA) toward finding a standard
voltage and redesigning servers to take "direct" power, or power
directly from a DC-based uninterruptible power supply (UPS), at a
standard voltage level in order to cut out this problem. Tschudi
said his group has yet to begin working with storage manufacturers,
but the issue of power conversions can be applied to virtually any
computer, both inside and outside, as today's motherboards also
perform multistep, inefficient conversions between voltage levels,
many of them based on outdated designs from the 1970s and 1980s
when chips needed multiple voltage levels.
Moreover, cutting down on conversions could be the closest thing
there is to a magic bullet when it comes to cutting down on power
consumption in the datacentre as a whole. "Even against the most
efficient of today's power supplies, direct power improved
efficiency 10% to 15%," Tschudi said. "Against the average
conversion system, you could be talking more like 20% to 30%, if
this is adopted on a wide scale."
The upshot for the storage market
Right now, it remains unclear which direction the storage
industry will move. Some vendors, like Sun Microsystems Inc., are
gung-ho about standardizing voltage levels within arrays as soon as
2.5-inch form factor drives are here.
"Right now, typically you have 5 volt and 12 volt conversions
within enterprise systems," said Chris Wood, chief technology offer
(CTO) of Sun's storage group. Wood said the higher voltage is
necessary to spin 3.5-inch drives at high rpms, but that once small
form factor drives hit the market, they will require smaller
engines, less voltage and could make the 12 volt conversion
obsolete.
"The whole industry is moving to small form factor drives," Wood
said. "This is one of the reasons why."
One storage vendor that's been playing an "observational" role
with LBNL's efforts, according to Tschudi, has been Network
Appliance (NetApp). "They've been observing this [conversion]
project and have done some work with us when it comes to improving
efficiency in their own datacentres through improved cooling
designs."
According to Brett Battles, director of storage product
marketing, "NetApp hasn't been heavily involved in LBNL efforts to
date. We are continuing to evaluate new power supply offerings, but
at this time we don't have any specific details to discuss, due to
the early stages of the evaluation process."
Hitachi Data Systems (HDS) is another major storage vendor
eyeing the direct-power option. "While it is early in the discovery
process, we are investigating the use of DC power and other
energy-saving alternatives," according to Claus Mikkelsen, chief
scientist.
The battle between reliability and efficiency
Not every storage vendor is sold on power conversion reductions
as a panacea. Storage system manufacturers Xyratex and Dot Hill
Systems Corp. already offer some systems designed for direct power.
However, according to Ken Claffey, product lead for power supplies
for Xyratex, reducing power in storage systems isn't as simple as
cutting out conversions, or even building a better power
supply.
"Storage systems are limited [in terms of power efficiency
development] by two things -- the need to power disk drives at a
high rpm and the need for redundancy and reliability."
Typically, in the interest of high availability, even the most
efficient power supplies are over provisioned for the highest load
in storage systems, even if it's twice the level the system really
needs. Xyratex is always looking for higher efficiency power
supplies, Claffey said, "but you have this battle between
redundancy and efficiency." Xyratex is currently looking into a
kind of dynamic load balancing for power supplies, which would
allow them to change voltage according to system workload.
Dot Hill also said there are better methods for reducing storage
power consumption than focusing on conversion. Among them, MAID,
which Dot Hill said it has in the works.
Whatever the method, it's clear storage vendors are scrambling
behind the scenes to catch up with their server counterparts, as
it's clear that users, as well as the government, are beginning to
take notice. The EPA submitted an energy efficiency report to
Congress in May focusing mainly on servers, but breaking out what
it called "first-order estimates" on storage devices. This
preliminary report also estimates that the energy costs of total
enterprise storage systems -- the networking, controllers and
switches that surround disk drives themselves, would be 50% higher
than the energy costs of the hard drives alone.
"The IT industry is a great beachhead for the DoE," he said.
"It's a relatively small group of companies that make up 1.2% and
climbing of the country's overall energy usage."