Description of problem:
The default image and instance folder is /var/lib/glance and /var/lib/nova, and it is easy to use up all the space. So add an option to let user choose would be better.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_hpdl388g805-lv_root
                       50G   47G     0 100% /
tmpfs                  20G     0   20G   0% /dev/shm
/dev/sda1             485M   64M  396M  14% /boot
/dev/mapper/vg_hpdl388g805-lv_home
                      848G   41G  765G   6% /home

+ service openstack-cinder-api start
Starting openstack-cinder-api: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-cinder-scheduler start
Starting openstack-cinder-scheduler: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-cinder-volume start
Starting openstack-cinder-volume: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-glance-api start
Starting openstack-glance-api: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-glance-registry start
Starting openstack-glance-registry: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-keystone start
Starting keystone: bash: line 0: echo: write error: No space left on device
[FAILED]
+ service openstack-nova-api start
Starting openstack-nova-api: bash: line 0: echo: write error: No space left on device
[FAILED]

Expected results:


Additional info:
nova have an "instances_path" option and glance have a "filesystem_store_datadir" option to config