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Linux allows you to use part of your RAM as a block device, viewing it as a hard disk partition. The advantage of using a RAM disk is the extremely low latency (even when compared to SSDs). The disadvantage is that all contents will be lost after a reboot.
Before getting started, let's find out the file system that our root partition uses. Run the following command (T - print file system type, h - human readable):
$ df -Th
The result should look like this:
Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 1.1G 0 1.1G 0% /dev tmpfs tmpfs 214M 3.8M 210M 2% /run /dev/sda1 ext4 218G 4.1G 202G 2% / <- root partition tmpfs tmpfs 1.1G 252K 1.1G 1% /dev/shm tmpfs tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs tmpfs 1.1G 0 1.1G 0% /sys/fs/cgroup /dev/sda2 ext4 923M 73M 787M 9% /boot /dev/sda4 ext4 266G 62M 253G 1% /home
From the results, we will assume in the following commands that the file system is ext4. If it's not your case, just replace with what you have:
$ sudo mkdir /mnt/ramdisk $ sudo mount -t tmpfs -o size=1G ext4 /mnt/ramdisk
tmpfs /mnt/ramdisk tmpfs rw,nodev,nosuid,size=1G 0 0
That's it. We just created a 1Gb tmpfs ramdisk with an ext4 file system and mounted it at /mnt/ramdisk. Use df again to check this yourself.
As we mentioned before, you can't get I/O statistics regarding tmpfs since it is not a real partition. One solution to this problem is using pv to monitor the progress of data transfer through a pipe. This is a valid approach only if we consider the disk I/O being the bottleneck.
Next, we will generate 512Mb of random data and place it in /mnt/ramdisk/file first and then in /home/student/file. The transfer is done using dd with 2048-byte blocks.
$ pv /dev/urandom | dd of=/mnt/ramdisk/rand bs=2048 count=$((512 * 1024 * 1024 / 2048)) $ pv /dev/urandom | dd of=/home/student/rand bs=2048 count=$((512 * 1024 * 1024 / 2048))
Look at the elapsed time and average transfer speed. What conclusion can you draw?