Hello stamac,   I'm sorry but only Dell Equallogic branded drives work in an EQL array.  There is custom firmware on the drive that the array looks for.   There's no workaround for this.   Regards,   Don 
We have an Equallogic PS4100x in production. Few days ago one of the drives failed and we ordered an original Dell HDD for this device. When we replaced the damaged one for the new one, the console says that the drive is not approved. We checked the documentation and just could find that that happens when there are firmware issues when the drives are not original (not coming from Dell) or are not alike. The other thing is that when I try to add it to the array, the option "Add to array" is gray out. Any help would be appreciate it, thanks!
One drive in the array is not approved