about zfs and ashift and changing ashift on existing zpool

[tech-lists]

Hello,

I have this in sysctl.conf on a desktop machine (12-stable):

vfs.zfs.min_auto_ashift=12

this has not always been there. I guess the zpool pre-dates it. I only
noticed it because have recently had to replace a disk in its zfs array
when I saw this:

% zpool status
pool: storage
state: ONLINE
status: One or more devices is currently being resilvered.  The pool
will continue to function, possibly in a degraded state.

action: Wait for the resilver to complete.
  scan: resilver in progress since Sun Apr  7 03:09:42 2019
        3.46T scanned at 79.5M/s, 2.73T issued at 62.8M/s, 3.46T total
        931G resilvered, 78.94% done, 0 days 03:22:41 to go

config:

NAME             STATE     READ WRITE CKSUM
storage          ONLINE       0     0     0
  raidz1-0       ONLINE       0     0     0
    replacing-0  ONLINE       0     0 1.65K
      ada2       ONLINE       0     0     0
      ada1       ONLINE       0     0     0  block size: 512B configured, 4096B native
    ada3         ONLINE       0     0     0
    ada4         ONLINE       0     0     0

What I'd like to know is:

1. is the above situation harmful to data
2. given that vfs.zfs.min_auto_ashift=12, why does it still say 512B
   configured for ada1 which is the new disk, or..
3. does "configured" pertain to the pool, the disk, or both
4. what would be involved in making them all 4096B
5. does a 512B disk wear out faster than 4096B (all other things being
   equal)

Given that the machine and disks were new in 2016, I can't understand why zfs
didn't default to 4096B on installation

thanks,
-- 
J.
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