Also anyone that has recommendations please reply 
Ive got a PowerEdge R900, default system setup. The problem was that the Perc6i Raid card only allows up to 2TB drives to be used. Also my system is using 3.5" drives so I only have 5 Bays available. I got this server to replace a custom built server that held (1) 2TB OS drive plus (8) 4TB Raid drives. Originally I was going to use a 2nd Adaptec raid card from the old system and convert it to use an external raid chassis, which would have worked but would have been an extra expense. So my layout would have been to use the Perc card for my OS and the 2nd raid for storage. I did end up doing that but saved a lot of expense by mounting (8) 3.5" drives in the PCI Bay area with a custom made mounting plate. I did lose all but 2 of my PCIe Slots because of space issues, I also had to remove the Drac Daughter-board from the NIC Board. Using 2 of the x8 Slots I installed a 8Port Raid Card and a 5port USB3.2 Card. I ordered (5) 900GB SAS drives for my OS Raid Drive (Raid 5) but in 2 Partitions to stay below the 2TB limit. I also used the (8) 4TB drives from the old File-server (Raid-5). I also Used a USB 3 External video card for HD Resolution, Notes at end. So here is the new server stats. Windows 2019 Standard x64 4 Quad Core CPU's 2.9Ghz ~16 Cores 64GB Ram Drive C - 1.7TB (Raid 5) Drive D - 1.5TB (Raid 5) Drive E - 25TB (Raid 5) 5 USB 3.1/3.2 Ports 4 Gigabit Ports (Teamed) VGA Out Video 1920x1080 This system has been up for almost 2 weeks with no problems. I have monitored temperature and speeds. Its running awesome. Now for some notes and recommendations. It would have been much easier and not to mention lighter to use 2.5" drives in the PCIe bay area and allow for more or all slots to be accessed, it also would allow for more airflow. I had 3.5" drives though and had to make it work. There is an internal USB 2.0 port that I recommend sticking a ~128GB flash drive in and making a backup of the server to that so you only need a restore CD to recover your server ICE (In Case of Emergency). You do not have to mount any drives in the rear of case. you can simply upgrade the Default Perc6i Controller with a replacement, its so easy. just install a 8x Adaptec or similar Raid card that supports the drive size you want. the connectors on the back-plane are standard SAS so you just have to get a ... to SAS cable, also remove the Perc Raid card from the system. Make sure your new raid card allows booting from it (unless you want to use a flash drive to boot from) I only have 2 raid cards I have tried but they work great. The Adaptec 5805 (Max (8) 4TB Drives) and the 6805 (Max (8) 6TB + possible) the notes say the second has drives supported up to 11TB but as I don't have any larger then 4TB right now I cannot confirm. The USB Video Card works great, it will work in a non USB3 port but limits resolution some to compensate for speed. But I wanted access to USB 3 anyways to plug a 10 Port USB 3 hub into and attach many 4 and 5TB external drives for backing up to this server with good speeds. I recently learned about NIC Teaming, its awesome just use YouTube to learn about it. HOME USE NOTES A server gets hot, lets face it, its a small super computer if configured with good options. They run great in a data-center as it has air conditioning and filtering. I am using this in my home, dust will be a problem. I used Cut-to-Fit air filters and installed them on the front air intake areas in front of the fans. Thank whoever designed this case there is a perfect gap for them. Also they are washable. I happen to have a Full Size Rack to mount my server and spent the extra for slide rails. If anyone wants a server without rack or rails, I would recommend help, these servers weigh about 100 pounds or more after Mods. Rails are a blessing. There is a cable management option for this server and I have it but am unable to use it due to Rack Depth. I Don't care for how it works, I've seen better but it does its job if you use it. I will be making a video of my work for anyone wanting to upgrade this model of server (YouTube). I got this very cheap but with its stats now is a fairly expensive server. I do wish it had a modern iDrac but that is a small item to miss as I don't mess with iDrac right now anyways. Also this does limit how many PCIe slots are available unless you use 2.5" drives, so if you need many slots and don't have small drives this wont work. Luckily this Mod works with multiple Dell servers, you just need a x8 Slot available and some DIY skills and perhaps no fear of frying a server (I cant guarantee your will work as mine did so take your own risks) If you are a company that has several of these, this would be a great option to upgrade and have a group that you could use for a test environment , perhaps many VMs? storage space? Off Network backup/storage? so many options for out of date equipment that can still perform like newer. This system is working so well, I have just ordered another one just like it. The new one I will not be mounting any drives inside, but will upgrade the raid card so that I can have a very large raid OS Drive. I will also be searching for a x8 Video card instead of the USB one, I will upgrade the USB to USB 3.2 also. and I think will also look for another 4 gigabit PCIe card so I can do NIC Teaming with 8 ports (my Cisco switch max team) I know that many normal users out there will not see this post but I know there are many Techs here that may benefit. And i hope that my information benefits this community. Last note: If anyone else has used other raid cards in dell servers, please post a reply with card model, ports, max drive allowed etc. I only have these adaptec's but would love to find others that support high TB drives and has drivers for new OS's      
PowerEdge R900 Upgrade to High Capacity Drives Greater than 4TB (Case Mod 
Optional) WORKS!