Hello.   Do you have any sever or applications jobs scheduled for weekend?   PERC 6i supports up to 2 TB of HD capacity no matter what HD capacity you use. Using HDs not certified by drives can lead to unpredictable issues as you have observed. I would suggest that you use Dell certified drives. 
I have a PE 2950III located at a datacenter that has a peculiar problem.  Know it is running in an "unsupported" configuration, so all bets are off in regards to "typical" issues.  It is running Windows Server 2013 Datacenter with Hyper-V and a few child VMs.  The only role on the host is the Hyper-V role and the VMs are all Windows Server 2016.  There are Storage Spaces set up on the server, and all 6 disks are configured RAID 0, which should be the same as presenting all disks as individual disks.  The Storage Spaces are working correctly.  The odd thing is that the server appears to spontaneously reboot, and *only on the weekends.*  When I use the DRAC to access the server, the PERC6i is showing a virtual disk is missing.  This is not really a problem since the redundancy of the disks are taken care of by Storage Spaces.  This is a storage repository, so performance is not at the top of the list for the server.  When they server restarts, it states that PERC 6i is missing Virtual Disk 0, which is actually the OS/Boot Disk so the server will not boot.  It does not show any Foreign Disks installed either. After the server is power cycled, the PERC 6i says that a foreign disk has been detected, and to press "F" to add it to the configuration.  Ones "F" is pressed, it boots normally, the VMs start, and all is well.  Does anyone happen to know what could cause the server to fail only on Saturday or Sunday, when it has the least load on it.  It is hung at the PERC BIOS screen.  Until the server is power cycled, it does not show any foreign disks present. The unsupported part - all of the disks are not Dell certified, and three of the disks are 3TB disks, which the PERC 6i reads as 2TB.  It appears to work fine in this configuration and does not complain about non-Dell disks used in the server.  I would like to know what event can occur to cause a crash and reboot the server,  The PERC driver for the 6i us reporting a predictive failure for disk 0:0:0, which I am replacing. I now I am venturing into uncharted territory and unsupported territory.  I am only hoping this will limp along until January 1 2017 The server appears to be shutting down gracefully based from the event log, as all services are attempting to stop before the shut down occurs, however after it shuts down, the RAID Controller stops the re-startup processes not recognizing Disk 0:0:0.  The event log does not that unsupported disks are installed, but not during boot.  I know that it is pertinent that I get off of this unsupported configuration ASAP, and that could not be more understood.  This server luckily is for backups of backups and not for LOB or important servers.All firmware is up-to-date.  Would it be possible that the 3TB disks are causing an issues (thought I personally don't see how they could) or is this a disk patrolling operation that is happening over the weekend the is crashing?If anything could toss any ideas into the ring I would certainly appreciate it.  Thanks!
Unusual problem with PE2950III with 2x Xeon 5450, 64GB RAM, PERC 6i