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Department of Electronics

Advanced Information Storage 18

Atsufumi Hirohata

17:00 05/December/2013 Thursday (P/T 006)

Quick Review over the Last Lecture

Millipede memory :

* http://nanotechweb.org/cws/article/tech/36334; * http://www.wikipedia.org/

Nano-RAM :

Floating junction gate :

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18 RAID and Cloud Computing

• Cloud computing

• Storage technology

• RAID

• Parity error detection

• Data striping

• Data mirroring

Cloud Computing

* http://www.wikipedia.org/

In 2006, Eric E. Schmidt (Google) first introduced the phrase : *

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Cloud Layers

* http://www.wikipedia.org/

Cloud computing extends the existing concepts : *

SaaS : Software as a service

PaaS : Platform as a service

IaaS : Infrastructure as a service

Cloud Companies

* http://cloudtimes.org/2011/11/30/top-paas-saas-and-iaas-cloud-companies-by-cloudtimes/

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Cloud for Mobile Devices Mobile data are stored in servers in cloud : *

* http://www.ubergizmo.com/2011/10/iphone-4s-review/

120 iPhones

1 server in cloud Can store data from

8 iPads

Storage Technology In 1987, David Patterson, Garth A. Gibson and Randy Katz defined : *

* http://www.wikipedia.org/; ** http://bnrg.cs.berkeley.edu/~randy/

Redundant array of inexpensive (independent) disks (RAID)

• combines multiple disk drive components into a logic unit

• Data distributed across the drives

• Levels of redundancy and performance required

→ RAID 0 ~ 10

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RAID 0

* http://www.wikipedia.org/

Block-level striping without parity or mirroring : *

•  Minimum number of drives : 2

•  Space efficiency : 1

•  Fault tolerance : 0

•  Array failure rate : 1 – (1 – r) n

•  Read performance : nX

•  Write performance : nX

Parity Error Detection

* http://www.computerhope.com/jargon/p/parity.htm

Parity bit is used for error detection : *

•  Even / odd parity

•  Binary stream contains even / odd number of “1”.

For example, serial data transfer uses

•  Binary stream : 7 digit + Parity : 1 digit

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Data Striping

* http://www.ni.com/white-paper/6253/ja/

Data stream is distributed to several drives : *

RAID 1

* http://www.wikipedia.org/

Mirroring without parity or striping : *

•  Minimum number of drives : 2

•  Space efficiency : 1 / n

•  Fault tolerance : n – 1

•  Array failure rate : r n

•  Read performance : nX

•  Write performance : 1X

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Data Mirroring

* http://www.openminds.co.uk/windows-solutions/data-replication/data-replicationmore-information.html

Data are duplicated onto another drive(s) : *

RAID 2

* http://www.wikipedia.org/

Bit-level striping with dedicated Hamming code parity : *

•  Minimum number of drives : 3

•  Space efficiency : 1 – 1 / n log 2 (n – 1)

•  Fault tolerance : 1 drive depending on the corresponding data and parity conditions

•  Array failure rate : variable

•  Read performance : variable

•  Write performance : variable

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RAID 3

* http://www.wikipedia.org/

Bit-level striping with dedicated parity : *

•  Minimum number of drives : 3

•  Space efficiency : 1 – 1 / n

•  Fault tolerance : 1 drive

•  Array failure rate : 1 – (1 – r) (n – 2) / 2

•  Read performance : (n – 1 )X

•  Write performance : (n – 1 )X

RAID 4

* http://www.wikipedia.org/

Block-level striping with dedicated parity : *

•  Minimum number of drives : 3

•  Space efficiency : 1 – 1 / n

•  Fault tolerance : 1 device

•  Array failure rate : 1 – (1 – r) (n – 2) / 2

•  Read performance : (n – 1)X

•  Write performance : (n – 1)X

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RAID 5

* http://www.wikipedia.org/

Block-level striping with dedicated parity : *

•  Minimum number of drives : 3

•  Space efficiency : 1 – 1 / n

•  Fault tolerance : 1 device

•  Array failure rate : 1 – (1 – r) (n – 2) / 2

•  Read performance : (n – 1)X

•  Write performance : (n – 1)X

RAID 6

* http://www.wikipedia.org/

Block-level striping with double-distributed parity : *

•  Minimum number of drives : 4

•  Space efficiency : 1 – 2 / n

•  Fault tolerance : 2 device

•  Array failure rate : 1 – (1 – r) (n – 3) / 2

•  Read performance : (n – 2)X

•  Write performance : (n – 2)X

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RAID 10

* http://www.wikipedia.org/

Mirroring without parity and block-level striping : *

•  Minimum number of drives : 4

•  Space efficiency : 2 / n

•  Fault tolerance : 1 device

•  Array failure rate :

•  Read performance : nX

•  Write performance : (n / 2)X