Evolution of External Disk Storage

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Evolution of External Disk Storage

• Nathan McIntosh

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What is Storage?

• Websters Dictionary
• Space for the safe keeping of goods.
• Examples of Storage
• Fridge/Freezer
• Shed/Garage
• For our purposes
• Direct Attached Storage (DAS)
• Network Attached Storage (NAS)
• Storage Area Networks (SAN)

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Direct Attached Storage (DAS)

• Where each server has dedicated storage, or
  attaching storage to individual computers
• Development Reason
• Necessity to expand storage space for the computer

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Ways to Attach DAS

• Integrated Device Electronic Cable (IDE)
• Ribbon cable with 40 pins
• Typically found connecting
• motherboard to maximum of two hard drives
• Small Computer Systems Interface Cable
• (SCSI) scuzzy
• Typically found connecting printers
• to computers
• Can connect up to 7 devices (newer SCSI version
  can connect up to 15)

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Ways to Attach DAS (Conted)

• FireWire Cable
• Single plug-and-socket connection
• Up to 63 devices attached
• Speeds up to 400 megabits per second
• Fiber Channel Cable
• Speeds of 2 Gigabits per second
• Yields 10 km of attenuation and approximately 126
  devices connected to it

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Problem with DAS

• Other computers could not access data remotely
• Floppy disk evolution
• Data redundancy
• Loss of time and money

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Network Attached Storage (NAS)

• Sharing data thru networks
• DAS is still attached to computer ? Computer now
  attached to LAN or WAN ? connected to server ?
  ability to communicate thru applications such as
  NFS or CISF

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Problems with NAS

• DAS Storage had to be local to the computer or
  appliance it was attached to

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Problems with NAS (Conted)

• External disk storage not independent, must add
  storage onto a computer or NAS appliance

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Storage Area Networks (SAN)

• SAN is a network of storage devices connected
  together serving multiple computers
• Theory came from printers

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Components of a SAN

• Fiber Channel Cable
• Host Bus Adapter (HBA)
• Fiber Channel Switch
• many-to-many relationships

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Benefits to SAN

• Separates LAN or WAN traffic
• Use of fiber channel cable
• Speeds of 200 megabits/sec (2 gigabits/sec)
• Frees up LAN lines
• Allows possibility to connect more computers
• Reduces administrative overhead cost
• Allows user to be able to use NAS with SAN
• Supports fiber channel tape drives

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SAN NAS Mixture
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SAN or NAS?

• SAN better choice
• Cost less in long run
• Ability to work with established NAS
• Reduces LAN overhead
• Faster rates of transfer
• Increases productivity
• Saving of time and money