Why at least 4 cylinder groups?

[Norbert Koch]

Am 2016-10-11 um 18:06 schrieb Konstantin Belousov:
> If your goal is reducing the memory consumption for the kernel and metadata
> overhead with the fixed amount of data to access, you may consider using
> tmpfs.  The additional kernel text size is tiny 50K, comparing with the
> 1.5M disk size.  If you mmap(2) the data from the ramdisk, then you will
> save the amount of memory twice the size of your mmaped data.
>
> tmpfs allows to set limits on mount, so you can have safety belts as well.

My ram disk is not a temporary storage. It is on a separate board 
equipped with
battery backed static memory. So tmpfs is not an option for me.