Sector-size and advanced format (4k) disks

Louie Cardone-Noott lcn at
Mon Sep 4 20:48:38 UTC 2017

Dear list,

I searched the handbook, archives, and web but couldn't find a concrete 
answer to this.

 From what I can work out:
1. for compatibility, most HDDs these days present themselves as having 
512 B logical / 4 k physical sectors
2. freebsd newfs (typically) sets a sector-size of 512 B and a fragment 
size of 4 k

Some questions then please. First, is it optimal to force the sector 
size to 4 k to match the physical sector size, or is the default (point 
2, above) fine? Second, how alarmed should I be that `man newfs` says 
setting the sector-size makes it impossible for fsck to find alternate 

I thought partitioning with (say) 1 M alignment and invoking newfs with 
`-S 4096` would be best. True or false?

Many thanks,

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