followup storage question

[William A. Mahaffey III]

On 09/11/15 09:31, Warren Block wrote:
> On Fri, 11 Sep 2015, William A. Mahaffey III wrote:
>
>> The Wiki page 
>> https://wiki.freebsd.org/RootOnZFS/GPTZFSBoot/9.0-RELEASE illustrates 
>> using gnop to enforce 4K alignment of gpt partitions for subsequent 
>> use by ZFS. However the gpart commands also use the '-a 4k' 
>> arguments, aligning partitions on 4k boundaries as I understand 
>> things. Is the gnop command also necessary ? TIA & have a nice weekend.
>
> These are two separate things.  gnop(8) is (was) used to force ZFS to 
> use a 4K block size.  That just means it transfers data in multiples 
> of 4K, not necessarily aligned with the 4K sectors on the drive. 
> gpart(8)'s -a flag is used to force partitions to begin in alignment 
> with the 4K sectors on the drive.
>

Hmmmm .... OK, however if I carefully 'gpart -a 4k' the underlying 
partitions aligned, then wouldn't the resulting ZFS above also be 
aligned ? I ask because the 2nd system I will be setting up in the next 
few weeks will probably use a RAIDZ1 on 6-8 partitions, & I have it on 
pretty good authority that you want RAID5-type storage properly aligned 
on the underlying drives or partitions. Thanks & TIA & have a nice weekend.

-- 

	William A. Mahaffey III

  ----------------------------------------------------------------------

	"The M1 Garand is without doubt the finest implement of war
	 ever devised by man."
                            -- Gen. George S. Patton Jr.