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Thriving in a Power Desert with Tape Storage

By Archive User posted Thu August 24, 2017 01:12 AM


Maximizing Hyperscale DC Revenue & Lifespan with Tape

Mike McIntosh & Shawn Nave

Problem: Unusable floor space tends to accumulate in older data
centers as they are upgraded to more powerful servers and storage that
consume more electrical power per rack. If the facility is maxed out on total power
and / or cooling capacity, migration to higher power density racks will result
in ‘power deserts’ – open floor space that cannot be used because there is
little or no power left to feed additional racks. The effect is illustrated by
the sagging sqft/m2 line on the right side of the figure below:

Floor space could be reclaimed for additional equipment if
the room power and cooling could be increased, but that requires infrastructure
improvements that may be impossible or prohibitively expensive for existing

The power desert effect is described by Timothy Morgan in his
account of Microsoft’s Columbia 1 & 2 data centers:

Back in the mid-2000s, when Columbia 1 and 2 were built,
server compute, storage, and power density was not what it is today, and so
now, with the Microsoft’s Open Compute Server platforms installed in these
facilities, only eight of the 18 rows have gear in them now, and because
Microsoft has substantially virtualized its networking inside the datacenter,
load balancers, switches, and routers are no longer in the facilities, either.
(It is a pity that the datacenter can’t have its power distribution upped to
5.7 megawatts and be filled to the brim again.)

Solution: Leverage the otherwise wasted floor space
by filling it with cold data stored on tape, which can be managed in an
automated tape library that consumes negligible power compared to a similar
footprint of high density servers. Co-location and cloud service providers may
substantially improve revenue / sq ft potential in older data center
facilities using this approach.

What sort of revenue gains are possible? Consider the
following hypothetical case, based on the example cited above where over 50% of
the floor space in a hyperscale data center is unoccupied.

Populate each empty equipment row with a single tape library,
configured as shown:

IBM TS4500 Tape library with 263 PB capacity:

drive & tape storage frames


redundant tape handling robots


TS1155 tape drives (360 MB/sec)


tape cartridges (15TB each)


Max continuous power (kW)


Data storage capacity of library (GB)


Assumed storage charge ($/GB/mo)


Potential revenue / library ($/mo)



Note that the entire library requires considerably less
electrical power (3.8 kW) and cooling than a single server rack, so it can live
in a power desert. In this hypothetical case if the data center has at least
38 kW of spare power, all 10 rows of open equipment space could be provisioned
with tape libraries, creating a total additional revenue opportunity of over

Capital costs of the library, tape drives and tape media
have not been included here. However, assuming an equipment life of 60 months (the
media can survive for decades), the capital costs are only a tiny fraction of
the total revenue potential and the payback is quick. Operating costs for
electricity and service are also negligible compared to the revenue potential.

Equipment life can be extended considerably beyond 60 months
and cartridge data capacity has doubled every 2.5 years since year 2000. Existing
TS4500 libraries can be concurrently upgraded with new generation tape drives
and media as they are introduced, permitting customers to increase both data
capacity and performance as the technology advances, without having to
reconfigure their floor space or buy a new library.