/tmp, /var/log, /var/tmp as /dev/md - why?

[Mattia Rossi]

Am 01.07.2014 21:27, schrieb Andreas Schwarz:
> Speed and speed, but I can't understand why using md here, there is already tmpfs,
> which optimzed for such cases (dynamic allocation, etc.).
>
> root at pizelot:~ # df
> Filesystem     1K-blocks    Used   Avail Capacity  Mounted on
> /dev/mmcsd0s2a    983680   57252  847736     6%    /
> devfs                  1       1       0   100%    /dev
> /dev/mmcsd0s2d   8106716 3068708 4389472    41%    /usr
> /dev/mmcsd0s2e   8106716  155976 7302204     2%    /var
> /dev/mmcsd0s2f   8106716236 7457944  <sip:2367457944>      0%    /home
> tmpfs            1097160       4 1097156     0%    /tmp
> tmpfs            1097160       4 1097156     0%    /var/tmp
>

On an embedded systems with little memory I prefer to limit the 
partitions to a certain size, like 32M, so dynamic allocation is no 
advantage. What other differences are there between tmpfs and a simple 
md device?
I'd be interested in knowing any tricks, that can make the system faster :-)

So yes, it's about speed. Especially mounting /var/log on development 
systems, where some errors can result in massive logging it's better to 
have that on a ramdisk rather than on the slow SD card.

Cheers,

Mat