10.1 + ZFS snapshot eating diskspace

[Rick Romero]

Try number two.   I built another new system, no encryption this time.

I replacated ONE snapshot that is about 562GB of data.
(I just found Ronalds reply in my Spam folder, sorry!)
This new 10.1 system has the exact same 3 drives in RAIDZ1 as the original
source (9.2).  What's confusing is the original RAIDZ1 is replicated
correctly to a 10 drive RAIDZ2 (10.1), but the RAIDZ2 source cannot
replicate data correctly to a new 3 drive RAIDZ1.
So not only is this a problem with the new system, but it concerns me that
if there were a problem with the old system that a full restore from backup
would eat all the disk space.

Source:
# zfs get all sysvol/primessd_home |grep -i used
sysvol/primessd_home  used                 
822G                   -
sysvol/primessd_home  usedbysnapshots      
260G                   -
sysvol/primessd_home  usedbydataset        
562G                   -
sysvol/primessd_home  usedbychildren       
0                      -
sysvol/primessd_home  usedbyrefreservation 
0                      -
sysvol/primessd_home  logicalused          
811G                   -

Right? 562 is the 'current' amount of space used? 

So I send it to a new box, and this is the result

# zfs list -t all
NAME                        USED  AVAIL  REFER 
MOUNTPOINT
sysvol                      919G      0  12.5G 
/sysvol
sysvol/home                 906G      0   898G 
/sysvol/home
sysvol/home at remrep-Week16  8.53G      -   898G  -

I can see a possible sector size diff or recordsize affecting a few bytes,
but 400G is a bit excessive. The fact that it more closely matches the full
dataset+snapshots, IMHO, is much more telling.

# zfs get all sysvol/home | grep used
sysvol/home  used                 
906G                   -
sysvol/home  usedbysnapshots      
8.53G                  -
sysvol/home  usedbydataset        
898G                   -
sysvol/home  usedbychildren       
0                      -
sysvol/home  usedbyrefreservation 
0                      -
sysvol/home  logicalused          
574G                   -

logical used is actual used, correct?   Why is it the 'full' amount, when
only one snapshot was replicated?

So I thought maybe it's not reporting correctly

# zfs list
NAME          USED  AVAIL  REFER  MOUNTPOINT
sysvol        907G  12.3G   256M  /sysvol
sysvol/home   906G  12.3G   898G  /sysvol/home

# dd bs=1M count=12560 if=/dev/zero of=test2
dd: test2: No space left on device
12558+0 records in
12557+1 records out
13167886336 bytes transferred in 33.499157 secs (393081126 bytes/sec)
# zfs list
NAME          USED  AVAIL  REFER  MOUNTPOINT
sysvol        919G      0  12.5G  /sysvol
sysvol/home   906G      0   898G  /sysvol/home
# dd bs=1M count=12560 if=/dev/zero of=test3
dd: test3: No space left on device

So what's going on?  Is this a known issue?
I suppose I can take the new server down to the colo and replicate from the
original, but that doesn't resolve the 'restore from backup' issue that I
see happening...