Warning message when trying to change Standby mode settings I tried changing the Standby mode settings using the command sudo pmset -a standbydelay 5400 . I set it to 5400 so that it is delayed to 1.5 hours compared to 70 minutes as default.

However, I get the following message right after I changed it :

Warning: Idle sleep timings for "Battery Power" may not behave as expected.
- Disk sleep should be non-zero whenever system sleep is non-zero.

What does this mean ?? Must I change the value back to 4200 ?

edit

Active Profiles:
Battery Power       -1*
AC Power        -1
Currently in use:
 standbydelay         5400
 standby              1
 halfdim              1
 hibernatefile        /var/vm/sleepimage
 darkwakes            0
 gpuswitch            2
 disksleep            0
 sleep                180
 hibernatemode        3
 ttyskeepawake        1
 displaysleep         5
 acwake               0
 lidwake              1
Based on the output of pmset -g, you have your system set to sleep after 2 hours, but the disk sleep timer is set to zero--meaning never according to the pmset man page. To correct the error, set disksleep to a value greater than zero but less than (or equal to) sleep.  

Use something like the following with your preferred disksleep time,

pmset -a disksleep 45


to set disksleep to 45 minutes for all power situations.  You may want to adjust these times for when your MBPr is running on battery.  Set battery profiles with -b instead of -a.  

I think you'll benefit greatly from the pmset man page. It's very clear and You'll probably discover something else that pertains to your needs there.