DAS, NAS and SAN

There are 3 most prevalent storage types that are primarily deployed by enterprises, which are  DAS (Direct-Attached Storage), NAS (Network-Attached Storage) and SAN (Storage Area Networks).

DAS

DAS is a traditional mass storage, the storage devices are directly/physically attached to the computer through an internal cable, which does not use any network. This is still a most popular approach. It provides block-level access through Small Computer System Interface (SCSI), Serial Advanced Technology Attachment (SATA), or Serial Attached SCSI (SAS), etc.

Advantages:

  • Storage device is dedicated with high performace compared to NAS
  • Lower cost,  inexpensive.
  • Simple to configure and use

Disadvantages:

  • Inability to share data or unused resources with other servers efficiently. This is addressed by NAS ans SAN but at the risk of security and higher initial cost.
  • Can not manage it by network
  • No high availability
  • Hard to expand storage capacity

NAS

NAS is mass storage attached to a computer which another computer can access at file level over a local area network, a private wide area network, or in the case of online file storage, over the Internet. NAS is commonly associated with the NFS and CIFS/SMB protocols. It is used to support shared info like documents, images, and videos.

Advantages:

  • Higher utilization with resource sharing
  • Scalable
  • Heterogeneous environment
  • Centralized storage with remote management
  • Save cost in the long run
  • Higher reliability in case of system failure or an outage,  easy-to-provide RAID redundancy to a large number of users.
  • Easy setup and configuration compared to SAN

Disadvantages:

  •  Limited scalability
  • Low Performance due to network issues.

SAN

SAN is a specialized network, that provides other computers with storage capacity. The crucial difference between NAS and SAN, is that NAS presents and manages file systems to client computers, while SAN provides access at block-addressing (raw) level, leaving it to attaching systems to manage data or file systems within the provided capacity. It offers the speed of DAS with the sharing, flexibility and reliability of NAS. SAN storage is a very sophisticated option that’s meant to support complex, mission-critical applications. SAN is commonly associated with Fibre Channel networks

Advantages:

  • Speed better than NAS
  • Resource utilization is similar to NAS
  • Terabytes of storage and multiple simultaneous access to files e.g. streaming audio/video.
  • Heterogeneous environment
  • Centralized Storage Management
  • High Degree of Fault Tolerance
  • Best and superior performance
  • Dynamic Scalability

Disadvantages:

  • More expensive than DAS and NAS
  • Implementation complexities.

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