Using RAM disk instead of a SD

[juranga]

Hi guys,

I have some problem writing a .csv file because it is not as fast as I need. I read that it is possible to save this file into the ram disk that could make the raspberry write faster. How could I get this? Which folder is the RAM disk of the RPi or do I have do another steps to perform this?

Many thanks!

[joan]

You have to create your own.

There are two steps.

1) create a mount point, e.g. mkdir /ram

2) create a sized RAM disk, e.g. sudo mount -osize=100m tmpfs /ram -t tmpfs

[fsr]

do I have do another steps to perform this?

yes, it's built into the kernel so easy to do

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$ sudo mkdir /mnt/ramdisk
$ sudo mount -t tmpfs none /mnt/ramdisk

unmount when finished to free up the memory

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$ sudo umount /mnt/ramdisk

edit: beaten

[juranga]

Many thanks for your answers!

I guess that ram memory is not volatile, isn´t it? Moreover, I have the RPI 2 so it has 1GB Ram memory, how could I know how many memory would be free to use in my things?

[GTR2Fan]

...how could I know how many memory would be free to use in my things?

Open a terminal and type...

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free

[JimmyN]

Many thanks for your answers!

I guess that ram memory is not volatile, isn´t it? Moreover, I have the RPI 2 so it has 1GB Ram memory, how could I know how many memory would be free to use in my things?

It is volatile, when you shutdown anything in there is lost to the outer darkness. If you want to keep what's there you'll need to copy it somewhere else before shutting down.

[jamesh]

Many thanks for your answers!

I guess that ram memory is not volatile, isn´t it? Moreover, I have the RPI 2 so it has 1GB Ram memory, how could I know how many memory would be free to use in my things?

It IS volatile - when the power is off, the data disappears. So you need to back the completed files off to SD card every now and again.

However, I don't think this is your problem, Baremetal I would write code that cached data then output to file in bigger chunks. But TBH, Linux should be doing that in the background for you in its file caching, so there is something off in your code somewhere that is slowing down writing to file.

[jahboater]

I guess that ram memory is not volatile, isn´t it? Moreover, I have the RPI 2 so it has 1GB Ram memory, how could I know how many memory would be free to use in my things?

Ram is volatile. Its contents are lost when the machine is shut down.
This implementation (tmpfs) uses "virtual" memory. It shares the available memory with other things such as applications and disk cache. The amount of memory used simply depends on the size of the files. The size given to mount is only a maximum (and it defaults to half the machines memory ). So "free -h" will show no extra memory used after you have created the disk (there is a slight overhead, about 100k, even if the filesystem is empty).

It is common to mount /tmp as tmpfs - just add this line to /etc/fstab

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tmpfs /tmp  tmpfs defaults,noatime 0 0

Which apart from being fast, is cleared out on reboot.

[juranga]

Many thanks for all your answers!

I cannot use the ram disk in my application but it is great to learn new things!