Storage Fundamentals

This post gives you an introduction to types of storage technologies and their usage.

Storage Basics

  • Data is a raw facts and conclusions are drawn from it

–Family photographs, handwritten letters, printed book, etc

  • Before computers were introduced, these data sharing were limited to paper and film
  • The same data could now be converted into forms like e-mail, e-book, etc and could now be generated from computers, etc. These are digital data(stored in strings of 0’s and 1’s)
  • With the advent of computers and communication technologies, there is an exponential rise in data generation and sharing
  • Data could be structured(organized in rows and columns) or unstructured(can not be stored in rows and columns)
  • Data created must be stored so that it could be easily accessible for further processing. Devices used for storing these data are termed storage devices or simply storage
  • Examples of storage devices are memory cards in cell phone, digital cameras, DVD’s, CD-ROMs, hard disks, etc.

Importance of Data

  • The importance of data in the modern world cannot be overestimated
  • Not only is data being stored by business but data is also mined to ensure business growth
  • There are now many mandatory laws which not only mandate data storage but also mandate on length of storage, mode of storage etc
  • In short, no major business in the modern world can run without a good storage strategy

Data Growth

  • Data has been growing rapidly in the past few years
  • It is estimated that the total data in the world doubles every three years !!!
  • The Internet revolution directly led to the data growth with every business going online
  • Many devices turning digital has also led to the data growth
  • Data is now stored all the way from a mobile phone to a mainframe
  • Government regulations have also ensured that data is stored for a longer interval of time
  • Amount of data generated by scientific programs is also increasing

Demands of Data

  • The demand on data is very high given its critical nature

–Data must be highly available

–Data must be secure

–Data must be reliable

–Speed of data access

–Data Recovery

Storage Topologies evolved the following way:

  1. DAS – Direct Attached Storage
  2. NAS/CAS – Network Attached Storage / Content Address Storage
  3. SAN – Storage Area Networks


DAS (Direct Attached Storage)

  • DAS is an architecture where storage attaches directly to the server
  • Two types of DAS are defined based on the location of storage device with respect to the host

–Internal DAS: Storage device is internally connected to the host by a serial bus or parallel bus

  • Supports limited number of devices
  • Occupies large amount of space inside host
  • Supports shorter distance for high-speed connectivity



–External DAS: Server connects directly to external storage device

  • Provides centralized management of storage devices
  • Eliminates distance limitation and device count limitation of internal DAS

Benefits of DAS

  • Low initial investment
  • Simple and deployed easily and rapidly
  • Fewer management tasks
  • Local data provisioning

Limitations of DAS

  • Single point of failure
  • Creates islands of storage since storage can not be shared
  • Limited scalability
  • Major management headache

–Each disk has to be backed up individually

  • DAS market is less but will not go away in a hurray


NAS (Network Attached Storage)

  • NAS is an IP-based file sharing device attached to a LAN
  • Network Attached Storage allows for distributed storage
  • Storage can be accessed over the network
  • Disks can be shared among multiple servers




  • NAS enables both UNIX and Microsoft Windows users to share the same data seamlessly.
  • In the generic topology, a central server acts as a file server (aka filer)

–Storage is attached to this server

  • Other servers on the LAN can access this storage
  • NAS device is optimized for file-serving functions such as storing, retrieving, and accessing files for applications and clients

NAS Components

  • NAS device has the following components:

–NAS head (CPU and Memory)

–One or more network interface cards (NICs), which provide connectivity to the network.

–An optimized operating system for managing NAS functionality NFS and CIFS protocols for file sharing

–Industry-standard storage protocols to connect and manage physical disk resources, such as ATA, SCSI, or FC



Benefits of NAS

  • It Supports comprehensive access to information
  • Improves efficiency
  • Improved flexibility
  • Centralizes storage
  • Simplifies management
  • Scalability
  • High availability – through native clustering
  • Provides security integration to environment (user authentication and authorization)

Limitations of NAS

  • When storage requirements grow very high, scalability becomes an issue
  • Single point of failure problem exists in NAS
  • Since NAS uses LAN, storage data shares bandwidth with other data
  • Certain applications, like databases, work best under block access
  • The speed of data access also depends on the processor in the NAS Appliance


CAS (Content Address Storage)


  • CAS is an object-based system that has been purposely built for storing fixed content data
  • It is designed for secure online storage and retrieval of fixed content.
  • The stored object is assigned a globally unique address known as a content address (CA).
  • CAS provides an optimized and centrally managed storage solution that can support single-instance storage SiS) to eliminate multiple copies of the same data

Benefits of CAS

  • Content authenticity
  • Content integrity
  • Location independence
  • Single-instance storage (SiS)
  • Retention enforcement
  • Record-level protection and disposition
  • Technology independence
  • Fast record retrieval


SAN (Storage Area Networks)


  • SAN is a Dedicated high speed network of servers and shared storage devices
  • SAN provides block level data access
  • SAN provides Centralized storage and management of data
  • It has high Scalability and Secure data AccessNext articles, I will discuss above SAN components and Zoning.