FAWN: A Fast Array of Wimpy Nodes

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FAWN A Fast Array of Wimpy Nodes

• Authors David G. Andersen et al.
• Offence
• Jaime Espinosa
• Chunjing Xiao

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Why FAWN Not

• A lot of research in parallel I/O
• They focus on workloads that are I/O, not
  computation, intensive.
• Electric cars consumes less power, but why you
  dont buy it?

• Increasing CPU-I/O Gap
• CPU power consumption grows super-linearly with
  speed.
• Dynamic power scaling on traditional systems is
  surprisingly inefficient

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Poor scaling characteristics

• The system includes a number of relatively high
  powered front-end systems
• Analysis has shown that for data-intensive
  workloads, large wimpy node clusters suffer from
  poor scaleup effects,
• Because they are more affected by a diminishing
  return scaleup effect than a smaller traditional
  cluster

Wimpy Node Clusters What About Non-Wimpy
Workloads (3.5.4 Discussion)
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Limitations(1)

• Only focus on read-mostly workloads (simple
  key-value workloads).
• They can not provide complex processing workload
  and it is bad for write-most workloads.

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Limitations(2)

• Works only for small data and small CPU
  work-loads
• Conclusions from author not going to replace
  current data-center, does not work for real-time
  applications (ie. gaming)
• Does not have ACID property that is desired in
  data bases (Atomicity Consistency Isolation
  Durability)

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Reliability problems

• More nodes hardware components leads to more
  failures
• less memory per node than traditional systems
• conversely more nodes are required for the same
  capacity.
• Communication, link and switch failure not
  considered

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Flash Problems (cost)

• Why did they only examine 3-year total cost of
  ownership (TCO) in Section 5?
• flash storage has short lifetime
• Flash is 15-20 times more expensive than HDD.
• the smaller flash cells are less reliable and
  less durable.

http//www.genomeweb.com/informatics/no-flash-pan
RETHINKING FLASH IN THE DATA CENTER
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Flash Problems (Size)

• The amount of physical space per megabyte is a
  problem
• Thermodynamically requires more energy
• It takes longer to heat a large room than a small
  one
• Environmental foot-print is relative to area
  needed

RETHINKING FLASH IN THE DATA CENTER
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Flash Problems (translation layer)

• Through heroic engineering and daunting
  complexity, the flash translation layer masks
  these problems, but its performance impact can be
  significant.
• Intels Extreme SSDs have a read latency of 85
  ms, but the flash chips the drive uses internally
  have a read latency of just 25 to 35 ms.
• Flash translation layer is part of the flash
  controller and is embedded in flash chips and
  drives

RETHINKING FLASH IN THE DATA CENTER
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Race Conditions

• Another study from CMU found that the system
  leads to race conditions
• dBug Systematic evaluation of Distributed
  Systems

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Conclusion

• It is a great system for quickly finding tiny
  amounts of data provided you have a lot of
  real-estate and dont mind the high probability
  of failure.

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Thank You