4K sectors on the drive, bigger sectors for geli and newfs?

[Pawel Jakub Dawidek]

On Wed, Apr 27, 2011 at 06:37:59PM +0200, Christian Baer wrote:
> Hi folks!
> 
> A few days ago I installed a new drive that I would like to encrypt with
> geli. It's one of the new ones with 4K sectors which means I have to
> partition it differently than the older drives I have.
> 
> What I did so far:
> 
>   gpart create -s gpt /dev/ad6
>   gpart add -b 2048 -t freebsd-ufs /dev/ad6
> 
> That should align the partition correctly.
> pjd wrote in a post, that geli uses more than one key for larger file
> systems, so I am quite happy to create a single (2TB) partion and file
> system.
> 
> Due to the nature of the files that will mostly be stored on the drive
> (digital photographs in raw format), my newfs will look something like
> this (my idea):
> 
>   newfs -L raw -O ufs2 -U -f 4096 -b 32768 -i 2097152 /dev/ad6p1.eli
> 
> An inode every 2^21 bytes should do fine. Most of the files on the drive
> (I expect something like 90%) will be 7MB or larger.
> 
> Any objections so far? Would it make sense to make the frags and blocks
> even larger?
> 
> Considering that, I'm wondering how to init geli, especially using the
> -s option.
> 
>   geli init -e aes-xts -l 256 -s $NUMBER /dev/ad6p1
> 
> It stands to reason that $NUMBER should not be smaller than 4096 bytes
> since the drive itself doesn't have anything smaller to offer. :-) What
> would be a good value? 4096 or 32768 or something else? What does this
> default to?

It defaults to reported sector size of the underlying provider, so 512
bytes, I guess. In my opinion 4096 is optimal. Larger sectors are
problematic, because if sector size it is larger than page size various
tools will have problems with mmap(2)ing files.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://yomoli.com
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