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 :
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 : *
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/
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
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
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
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
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
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