# RAD Drive?



## zader (Nov 16, 2020)

HI all

In short .. once upon a time on my Amiga, one could create a RAD (recoverable ram drive) and modify the system start up sequence to copy workbench (the os) directly into RAM ..

the basic idea of RAD is
A: ram is much faster than disk
B: the key RAD feature is that it will survive a warm reboot
C: formatting memory into a container / volume that can be mounted as a "storage device"

Here is some more information..  (and yes its from 1993) 

RAD

My thought was the concept has a lot of appeal/potential especially when combined with modern features like; zfs, jails, volumes, replication and even "pools" of ram...  or even a high speed zvols / caching  that can survive reboots, be replicated at will.


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## SirDice (Nov 16, 2020)

On the PC the contents of RAM is erased during boot. So the data simply cannot survive a warm boot. The Amiga also had much of its system baked in ROM, most of the important libraries at least and it didn't erase the RAM contents with a warm boot.


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## zader (Nov 16, 2020)

I forgot about that ..  wonder if we can fit freebsd on a 16k rom chip...


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## richardtoohey2 (Nov 16, 2020)

Isn't this a bit like suspend/resume on laptops?  It's not quite turned off, so should come back quicker.  But I think the machine state is stored on secondary storage, so still needs time to be read back into RAM.


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## ralphbsz (Nov 17, 2020)

In a nutshell, there is no need to copy the whole disk into RAM. Instead, you only copy the parts that are likely to be read again. And all modern file systems do that already, it's called caching. There are lots of optimizations on how to use memory most efficiently, and how to balance between file system cache and other uses of memory. So at any given moment, if there is a good reason for part of the root file system to be in RAM, it should be.


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