I am currently using the erase free space feature on my Mac (os Yosemite.) I am using the 36 pass security feature to make sure some deleted financial logon data is secure. (Probably overkill, but...) I have around 1/2 of 1 terrabyte disk with free space. Any rough idea of how long the process should take; I have 12 gig memory total and about 4-5 free. The other programs, when I am running any, seem to work OK and not significantly slowed down. I am still on my first pass after around 3 hours, but the program seems to be running and not taking a lot of resources according to my activity monitor. I don't mind leaving my Mac running constantly for a few days, if that is what it takes? Do I have to set my sleep setting to "never" or will the program prevent my Mac from sleeping while it is running. The program says that it can't be stopped, but I assume it means that it will leave a file if it is forced shut etc. I have read the message just above this one about a reboot.
Thanks; just wanted to make sure that the warning about taking several hours can mean DAYS.