Quick Answer
Yes, it is perfectly okay and quite common to have 3 hard disk drives (HDD) installed in a PC. Many desktop computers have space and power supply capacity for up to 3 or 4 HDDs. Reasons to use multiple HDDs include needing extra storage capacity, separating the operating system from data, having drives optimized for different uses like SSD for OS and HDD for data, and allowing for redundant backups. As long as your power supply can handle it, there are enough drive bays and SATA ports, and your motherboard supports that many drives, using 3 HDDs in a PC is a very common and effective storage configuration.
More Detailed Answer
Using multiple hard drives in a desktop computer provides a number of advantages:
Extra Storage Capacity
The most obvious benefit of having 3 HDDs is being able to have much more storage capacity than a single drive could provide. For example, combining two 4TB HDDs with a 2TB HDD would provide a total of 10TB of storage space. This is far more capacity than even the largest consumer single drives on the market today.
For users who work with large files like high resolution photos and videos or just need tons of general storage space, using multiple hard drives is an effective way to add terabytes of capacity. It is much cheaper to add extra HDDs than replacing a single drive with a larger one.
Separating OS and Data
Another common reason to use multiple drives is keeping the operating system separate from data storage. The OS drive is best as a fast, low capacity SSD, while data drives can be higher capacity traditional HDDs.
Installing the operating system like Windows on an SSD results in much faster boot and loading times compared to a HDD. But SSDs are more expensive per gigabyte than HDDs. So using a smaller 250GB or 500GB SSD for the OS drive, paired with 1TB+ HDDs for data storage provides the best combination of speed and storage capacity.
Keeping the OS separate from data also makes managing, backing up, and potentially reinstalling the OS simpler. The data drives can be easily retained while the OS drive is wiped and refreshed as needed.
Optimized Drives
With multiple drive bays, users can optimize each drive for specific purposes. As mentioned above, using an SSD for the operating system provides great performance, while large capacity traditional HDDs store data.
But there are other options too. You could set up a drive optimized for gaming storage by using a hybrid SSHD drive or a fast SATA SSD. Another drive bay could hold a NAS optimized drive meant for 24/7 operation in a RAID array. External drives connected via eSATA can add even more options like backup drives.
Having multiple drive bays allows mixing and matching drives to optimize storage for different purposes.
Redundant Backups
Data backup is crucial for protecting against data loss from drive failures, accidental deletion, corruption, hacking, and disasters like fires or floods. With multiple drives available, users can configure redundant backups for maximum protection.
A common simple option is to manually copy important data periodically from the main data drive to a second backup data drive. This provides a redundant copy if one drive fails.
More advanced options include RAID 1 mirroring to automatically copy data to two identical drives in real-time. Or an automated backup program can copy files to multiple drives for versioning and redundancy.
Multiple HDDs allow creating onsite backups that are immediately available when needed and protect against drive failure. External drives add another layer for offsite protection.
Faster File Access
Using multiple drives can also improve general file access speeds similar to a RAID 0 striped array. Data can be split and accessed simultaneously across multiple drives for faster read/write times vs a single drive.
So three HDDs striped together can provide roughly triple the real-world transfer speeds of a single HDD for large files like videos, photos, and games. This makes working with and backing up huge amounts of data much faster.
Of course, RAID 0 striping does not provide any redundancy. But combining striping for speed with a mirrored backup drive or online backup provides the benefits of both speed and protection against drive failure.
Requirements for 3 HDDs
The main requirements for running 3 HDDs in a desktop PC are:
Adequate Power Supply
HDDs require relatively little power, typically 5-10W each under load. But multiple drives add up, so you need a beefy enough power supply. A quality 500W+ unit is recommended for a system with 3 HDDs to provide plenty of headroom. Multiple GPUs or other power hungry components may require even larger power supplies.
Available Drive Bays
The computer case and motherboard must provide enough drive bays and mounting points for 3 HDDs. Most mid and full tower cases have space for up to 4-5 HDDs. Smaller form factors may only fit 1-2 drives.
Open SATA Ports
There must be enough open SATA ports coming off the motherboard to connect 3 drives. Most motherboards have 4-6 SATA ports, but be sure to check before buying drives. Add-in SATA cards can expand the number of available ports if needed.
OS Drive Support
The motherboard and OS need to be able to properly detect and utilize all 3 connected HDDs. This is not usually a problem for modern Windows, Linux, and Mac OS systems. But very old OSes may not work right with that many drives.
As long as those requirements are met, there should be no issues installing and running 3 HDDs in a desktop PC.
Drive Bay and Mounting Options
Where and how the hard drives are mounted in the computer can vary quite a bit depending on the case and drive bay configuration:
Internal Bays
Most cases provide dedicated internal 3.5″ drive bays to securely mount full size HDDs. These bays slide out for easy drive access and swapping. They include the necessary SATA power and data cables to connect the drives to the motherboard and PSU.
2.5″ Bays
Some cases now include dedicated bays for mounting smaller 2.5″ SSDs and laptop HDDs. These allow combining 3.5″ and 2.5″ drives for a mix of high capacity HDDs and fast SSDs. Adapter brackets can also let a 2.5″ drive fit into a 3.5″ bay.
5.25″ Bays
Optical disc drives are less common today, so 5.25″ external bays often go unused. 5.25″ to 3.5″ drive bay adapters can convert these into spaces for additional HDDs.
Backplane Mounting
In higher-end gaming and workstation PCs, the HDDs mount into a backplane inside the case. This simplifies swapping drives in and out. Cases like the Corsair Obsidian 900D support up to 6 backplane mounted HDDs.
External Enclosures
If the PC case itself lacks sufficient bays, external hard drive enclosures provide a simple solution. These enclosures fit multiple 3.5″ drives and connect via eSATA or USB 3.0 to add extra storage capacity. In some ways these external enclosures can provide more flexibility for drive access and swapping compared to internal bays.
With all these mounting options, finding a good home for 3 HDDs inside virtually any PC case should be straightforward.
Recommended Drive Combinations
If setting up a system using 3 hard disk drives, here are some recommended drive configurations:
SSD OS Drive + 2 HDDs
An ideal balance of speed and storage capacity:
– 250-500GB SSD for OS, applications, and some games
– 2 x high capacity (4TB+) 7200 RPM HDDs for data storage
With the OS on a separate SSD, the two HDDs can be set up in a RAID 1 mirror for redundancy or stripped for extra speed.
SSD OS + SSD Games + HDD Storage
The ultimate setup for a high performance gaming rig:
– 500GB NVMe SSD for OS and core programs
– 1TB SATA SSD dedicated for games
– 4TB or larger HDD for pictures, video, documents, backups, etc.
Very fast boot and game launch times thanks to the dedicated game SSD, plus tons of HDD capacity for everything else.
SSD OS + SSHD + HDD
A good middle ground combination:
– 250-500GB SATA SSD for OS, apps, main games
– Firecuda or other 1TB+ SSHD for games and scratch storage
– 4TB or bigger HDD for data storage
Benefits from the SSHD’s faster speeds compared to a pure HDD, while still getting lots of cheaper high capacity storage.
Example Builds
Here are examples of real PC builds that utilize 3 HDDs in different configurations:
Ryzentosh Creator Workstation
A hackintosh built for video editing and content creation using a RAID 5 array for storage:
– 500GB Samsung 970 Evo NVMe SSD – macOS, Apps, Scratch space
– 3 x 8TB Seagate Barracuda HDDs – 24TB RAID 5 Array
– AMD Ryzen 7 3700X CPU, AMD RX 5700 XT GPU, 32GB RAM
With huge RAID array for active project files and exports, plus fast NVMe SSD for system drive. Great for Final Cut Pro, Premiere, and other creative software.
ROG Strix Gaming PC
A high end Asus gaming PC with dedicated game storage:
– 512GB Samsung 960 Pro M.2 SSD – Windows, core apps
– 2TB Intel 660p M.2 SSD – Game library
– 3TB Seagate Barracuda HDD – Media storage
– AMD Ryzen 7 5800X, NVIDIA RTX 3080, 16GB DDR4 RAM
Excellent for high fps 1440p or 4K gaming. 2TB of fast SSD storage for games, plus high capacity HDD for everything else.
Fractal Design Budget Build
An affordable mid-range home and office PC:
– 240GB Kingston A400 SATA SSD – Windows, Office, browsers
– 1TB Seagate Barracuda HDD – Applications, documents
– 2TB WD Blue HDD – Media files, backups
– Intel Core i5-10400F, GeForce GTX 1650, 16GB RAM
Reliable and responsive for everyday multitasking, spreadsheets, web browsing. Plenty of HDD space for large media libraries.
These showcase just a few examples of the many ways 3 HDDs can be leveraged in typical PC builds and setups. Whether you need maximum gaming performance or just lots of affordable general storage capacity, running 3 hard drives is a straightforward way to meet a system’s storage needs.
Conclusion
Installing and running three hard disk drives in a desktop computer is perfectly normal and provides unique advantages over relying on just one or two drives.
Extra drive bays allow adding storage capacity, separating the operating system from data, optimizing drives for specific purposes, creating instant data backups, and improving performance through disk striping.
As long as the power supply has sufficient wattage, the case has enough drive bays and mounting options, and the motherboard supports multiple drives, a 3 HDD setup should work great for just about any usage, from gaming rigs to home office PCs.
Carefully considering the optimal drive combination, such as an SSD for OS and games paired with large HDDs for data, can maximize both speed and overall storage capacity. For power users that need lots of fast storage, running 3 HDDs is an easy way to get the storage space and performance desired out of a desktop computer system.
