Q: Failed to create 2nd partition

running OS X 10.8.5

tried to create a 2nd partition for El Capitan

booted in recovery partition

opened disk utility

clicked the ( + ) to create a new partition

started partioning

said shrinking disk

crashed - had to force restart

booted in single user mode

run fsck -fy

repaired disk

tried partioning again

after a long time a message said it didnt create the partition

of course now i m even more afraid to upgrade ...

is there sth wrong with my HDD ? could it be it has data written all over the place ?

( OS X 10.8 was a clean install after a failed upgrade)

anyway, is there any way to partition this drive ? ( clean install of El Cap would be nice but its not worth it since it could be too slow for me  - early 2009 iMac)