Re: Small device

[Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>]

Hi,
On Thu, 10 May 2012 00:33:30 +0100, Zeke Rondel wrote:
> Hi,
> 
> I've a small memory card (SD) of 64MB used for keys related to crypto.
> stuff so I need a log filesystem that avoids the data can be re-written
> or modified. Is NILFS suitable in case of little devices? If so, which
> size of blocks per segment would be suitable for it? Thanks in advance!

Basically NILFS is not designed for small devices.  Its most on-disk
data items have 64-bit width.  In addition, it's more likely to suffer
from disk full on such devices due to the copy-on-write nature.

However, I guess you can use NILFS on 64MB SD card by formatting the
device with a smaller block size and a smaller number of blocks per
segment.

My mkfs format parameter for a 64MB sized device is as follows:

$ mkfs -t nilfs2 -b 1024 -B 512 <device>


We may get more disk space overhead for much smaller "blocks per
segment" because every segment of NILFS needs at least one header
block.


Regards,
Ryusuke Konishi
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