imho the problem is greatly overrated.
there is nice short doc from IBM dev
http://www.ibm.com/developerworks/linux ... tor-disks/.
on mac you have aligned partitions since 2006 (at least)
http://developer.apple.com/library/mac/ ... index.html.
zfs is using blocks with size < fs block size only for object below fs block size. if over, it uses fs blocks, look here for files with size 1byte, 128k and 128k+4k. and RMW will happen only on writes of files < 4k. this is clearly seen from the IBM doc.
file big 1byte:
Object lvl iblk dblk dsize lsize %full type
7 1 16K 512 4K 512 100.00 ZFS plain file
168 bonus System attributes
file 128k:
Object lvl iblk dblk dsize lsize %full type
9 1 16K 128K 128K 128K 100.00 ZFS plain file
168 bonus System attributes
file 128k+1:
Object lvl iblk dblk dsize lsize %full type
10 2 16K 128K 264K 256K 100.00 ZFS plain file
168 bonus System attributes
linux fdisk is aligning since jan-2012.
you can destroy and realign the filesystems how much you wan't, with dd and large file working sets you will never be able to measure difference - thinking of situation, that your fs are using zfs on disk or slice created by mac with os never than 10.4.