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What is an ramdisk and How ramdisks can be created. (Doc ID 2349947.1)

Last updated on OCTOBER 20, 2022

Applies to:

Oracle Cloud Infrastructure - Version N/A and later
Linux OS - Version Oracle Linux 5.0 and later
Information in this document applies to any platform.


*) What is a ramdisk

The RAM disk drive is a way to use main system memory as a block device ( Memory used as Disk partition to store data ). It is required for initrd, an initial filesystem used if you need to load modules in order to access the root filesystem. This can be the RAM disk device itself, or an unused disk partition (such as an unmounted swap partition).

*) What are some of the other uses of the RAM disk.

It may have other uses. It can also be used for a temporary filesystem for crypto work, since the contents are erased on reboot. One of the adventages to use this as data store is that the files stored inside ramdisk partition will have the faster access as compared to hard drive as memory is faster than disk. It will help to increase the performance if some data is accessed constantly.

*) What is tmpfs.

Just to other options; Tmpfs is an alternative of Ramdisk as it's a file system which keeps all files in virtual memory. Everything in tmpfs is temporary in the sense that no files will be created on your hard drive. If you unmount a tmpfs instance, everything stored therein is lost. If you compare it to ramfs (which was the template to create tmpfs) you gain swapping and limit checking. Another similar thing is the RAM disk (/dev/ram*), which simulates a fixed size hard disk in physical RAM, where you have to create an ordinary filesystem on top. Ramdisks cannot swap and you do not have the possibility to resize them.

*) How to create a ram disks

In order to create a Ramdisk some values need to be added in the grub.conf of the Server.

*) One example to use :

The application requirements needed one 16GB ramdisk but the kernel is defaulting to sixteen 16MB ramdisk. 


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