[LEDE-DEV] (short) file length

[Stephan Hennig]

Hi,

in sector oriented file systems, files slightly larger than sector size
(or some other base unit) usually cause unused (waste) space in a file
system.  LEDE uses compressed file systems.  Is there any such thing as
a "sector size" in LEDE one may take into account

  i) when creating files while running LEDE

  ii) when placing files in an image using the image generator?

An example are client keys stored in /etc/dropbear/authorized_keys.
Here are some numbers for RSA client keys:

  private key length     public key file length

    2048 bits              ca. 400 bytes
    2600 bits              ca. 500 bytes
    3000 bits              ca. 550 bytes

For uncompressed file systems with a sector size of 512 bytes, client
key length of 2600 bits looks like a good compromise between security
margin and memory consumption.  But how does that reasoning translate to
LEDE (OpenWrt)?  Targeting memory constrained devices, say, 4 MB Flash +
16 MB RAM, is there any advantage in tuning file length to
some file system characteristics?

Best regards,
Stephan Hennig