rrdcached + gmetad :: Permission denied nightmare

Hi! I am trying to make rrdcached work with gmetad (centos 7 + systemd)
but not matter what i tried i get the same permission denied messages :
RRD_create: rrdcached: Permission denied

rrdtool is 1.7.0 rebuild by me (somehow ... each time is black magic as 
the included spec never works on centos)
so, for rrdcached i have :

[root@monitor rrdcached.service.d]# cat override.conf
[Service]
PIDFile=/var/run/rrdcached.pid
UMask=0002
ExecStartPre=/usr/bin/umask 0002
ExecStart=
ExecStart=/usr/bin/rrdcached -g -a 16 -t 8 -w 2m -j 
/var/tmp/rrdcached-journal -U ganglia -G ganglia -s apache -m 777 -P 
FLUSH,STATS,HELP,INFO -l unix:/tmp/rrdcached_lim.sock -s ganglia -m 664 
-l unix:/tmp/rrdcached.sock -p /var/run/rrdcached.pid
WorkingDirectory=/tmp

[root@monitor tmp]# ll rrd*
srwxrwxrwx. 1 root apache  0 Dec  1 22:41 rrdcached_lim.sock
srw-rw-r--. 1 root ganglia 0 Dec  1 22:41 rrdcached.sock

and for gmetad :
[root@monitor gmetad.service.d]# cat override.conf
[Service]
Environment=RRDCACHED_ADDRESS=unix:/tmp/rrdcached.sock
UMask=0002
ExecStartPre=/usr/bin/umask 0002
ExecStart=
ExecStart=/usr/sbin/gmetad --pid-file=/var/run/gmetad.pid 
--conf=/etc/ganglia/gmetad.conf

[root@monitor gmetad.service.d]# grep username /etc/ganglia/gmetad.conf
setuid_username "ganglia"

[root@monitor gmetad.service.d]# grep rrd_ /etc/ganglia/gmetad.conf
rrd_rootdir "/home/ganglia-rrds"

[root@monitor gmetad.service.d]# ll -d /home/ganglia-rrds
drwxrwxr-x+ 11 ganglia ganglia 4096 Dec  1 22:51 /home/ganglia-rrds

[root@monitor gmetad.service.d]# ll -1 /home/ganglia-rrds
total 72
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 EMI_CORE
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 EMI_WNs
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 ISS-AF
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 ISS-ALICE
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 ISS-Planck
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 ISS-RoSpaceGRID
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 Misc
drwxr-xr-x+ 2 ganglia ganglia 4096 Dec  1 22:51 __SummaryInfo__
drwxr-xr-x+ 3 ganglia ganglia 4096 Dec  1 22:51 XROOTD

Any idea what am i missing? it is puzzling as everything is the same 
user and group so i have no idea from where i get
RRD_create: rrdcached: Permission denied

moreover it seems that the error come from file creation as directories 
for servers/devices are created...

i need the functionality of rrdcached as
this is an old 4 core opteron that stays at 20% load with ~2.3 MiB 
constant writes .. i could move the rrds to ssds but i want first to see 
if i can avoid the ssd usage.

(yes, without rrdcached, gmetad works without problem)

Thank you!!
Adrian