What is a software RAM disk?

RAM disk is a portion of the Random Access Memory (hardware RAM) that is configured such that it is treated as a disk drive by the computer. The access time to a RAM disk is much faster than accessing data on the physical hard drive.

Since the RAM disk is a simulated hard drive saved in the Random Access Memory, its contents are lost if the computer is turned off.

The RAM disk is also termed as a ‘virtual disk’ or a ‘RAM drive’. RAM disk support is built into Linux kernels since version 2.4. RAM disks always have fixed sizes.

Why do we need a RAM disk?

  • Due to substantially faster access times, RAM disks are extremely popular with applications that require frequent access to data. For example:
    • A web cache can be on a RAM disk. The web server has to cater to substantial number of requests every second and having the contents to be served in a RAM disk has multiple advantages.
      • The IO is considerably reduced, since the web content to be served is read into the RAM disk only once and all the successive requests are served utilizing the cached content.
      • There would be considerable improvement in the response time of the web server since it does not have to access the secondary storage device.
  • Since the contents of the RAM disk are lost if the system is turned off, RAM disks are very useful for applications that regard privacy with utmost importance. For example:
    • RAM disks can be used to work with unencrypted content of a encrypted file. This way, the unencrypted contents are never written to any physical media which would otherwise be a concern.
  • A complete secondary storage less machine is a possibility with the RAM disk concept. For example:
    • RAM disks are used by live CD distributions to mount loop back file systems.
      • Therefore, even though the operating system is loaded off a read-only optical media, the user can create and edit files.
      • These file are volatile and would be erased if not saved to a physical medium before the system is powered off.

Resources:

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