Effect of partitioning on wear-leveling

[bob prohaska]

On Mon, Mar 21, 2016 at 01:01:24PM -0600, Ian Lepore wrote:
> 
> Freebsd does no wear-leveling, it's up to the microcontrollers within
> the storage devices to do that.
> 
> Those controllers have no notion of partitioning or filesystem layout
> and do whatever they want to do internally about wear leveling.  That
> leads to the mildly disturbing situation of having blocks from a
> readonly filesystem and blocks from a writable filesystem sharing the
> same flash erase-block inside the device.  One likes to think of the
> data in a readonly filesystem as safely protected from the read-modify
> -write activity that happens at the flash erase-block level, but no
> such g'tee is made on any mmc, sd, or usb flash-based devices I know
> of.
> 
> - Ian
> 
Ok, thanks. It sounds like /var and /tmp could be confined to limited-size
partitions while still permitting wear leveling to use other, less-used
parts of the device. So, if a block nominally in /var reaches end of life
can the wear leveling controller start stashing data anywhere on the device? 

As a practical matter, should I even be worrying about this? Folks once
made a big deal of partitioning storage so a runaway process couldn't 
choke the whole machine. Is the precaution still worth taking on ARM?

bob prohaska