unclean shutdown and space cache rebuild

[Shridhar Daithankar <ghodechhap@ghodechhap.net>]

Hello,

I have 3 partitions with btrfs(/, /home and /data). All of them have following 
mount options

noatime,space_cache,inode_cache,compress=lzo,defaults

Whenever there is a unclean shutdown(which happens a lot in my case), the next 
reboot, system comes up relatively at the same speed but as systemd is 
starting up daemons, the disk is continuously ( and unusally long) grinding.

This causes random delays with various daemons such as postgresql failing to 
start, kdm timing out of xorg servers etc and I have to reboot after the dust 
settles to bring back the system to the normal. At one time, even 
keyboad/mouse were not responding as some debus service timed out..

I think it is rebuilding the space cache because I saw similar long disk 
activity when I activated it first.

How can I confirm that it is the space cache rebuild thats taking time?

if space cache rebuild is the reason, is there any way to improve it? 

I am running archlinux/systemd/kde setup with two 7200 RPM seagate sata 
disks(no RAID, one 80 GB for / and /home, other 500GB for data). The kernel is 
3.9.8 x86_64.

Thanks.

-- 
Regards
 Shridhar