Quick overview of nas vs san and file-level vs block-level storage

In this quick overview we will look at basic definitions of NAS and SAN and also compare advantages of file-level vs block-level storage.

NAS arrays are based on file-level storage. In this type of storage, the storage disk is configured with particular protocol (NFS, CIFS, and so on) and files are stored and accessed from it as such, in bulk. NAS is can be described as a bunch of disks arranged in a Raid and consisting of either SAS (serial attached SCSI) or Sata disks.

SAN arrays are based on block-level storage. The raw blocks (storage-volumes) are created, and each block can be controlled like an individual hard drive. Generally, these blocks are controlled by the server-based operating system. Each of this block storage volumes can be formatted with file system of your choice.File-level storage advantages. SAN allows multiple servers to share a pool of storage. It making it appear to the server as if it were local or directly attached storage.


File-level storage systems more suited for bulk file storage.

  • Can be configured with common file-level protocol like NTFS or NFS
  • File-level storage is easy to setup and implement
  • Stores files and folders and makes them visible to system storing them and accessing them
  • In most cases they are much less expensive
  • File-level systems are more popular with NAS systems.


Block-level storage advantages

  • Each block or storage volume can be treated as independent disk drive and is controlled by external OS
  • Block-level storage systems offer better speed and performance specially for virtualization
  • Each block or storage volume can be formatted with the file system required by the application – NFS,NTFS,SMB
  • Block-level storage very popular with SAN
  • Block-level storage systems are more reliable, and there transport systems are very efficient
  • Then support external boot of the system connected to them
  • Block-level storage can be used for special applications like databases and virtual machine file systems


File-Level Protocols

File-level protocols are used to read and write variable-length files. Files are segmented into blocks before being stored on disk or tape. Common Internet File System (CIFS) and Network File System(NFS) are file-based protocols that are used for reading and writing to files across the network. CIFS is Windows based protocol and can be implemented on Linux/Unix based systems via SAMBA. NFS is protocol that would be used on Linux/Unix based system.
The file-based protocols are best suited for file-based applications. MS Office, SharePoint and so on just some of the examples.