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List:       linux-nilfs
Subject:    Re: Small device
From:       Zeke Rondel <zeke () mailup ! net>
Date:       2012-05-10 18:01:55
Message-ID: 1336672915.6952.140661073861013.227CE5BB () webmail ! messagingengine ! com
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On Fri, May 11, 2012, at 12:42 AM, Ryusuke Konishi wrote:
> 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.
Using "-b 1024 -B 512", we would get 512 blocks per segment: (1024*512)
/ 1024

Then, what about to use "-B" to 1024 or to 2048 ? So there were lesser
number of full segments in the device.
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