It seems like you can never get enough storage on your computer.
No matter how large of a hard drive you get, it always fills up quickly, and you don’t want to have to delete your precious files and games.
One logical solution is to use two hard drives to double your storage.
You can also use some of the extra storage to back up your most critical data.
However, what if the second one also fills up?
Can you install a third one? Is there a limit on the number of hard drives you can add to a PC?
How Many Hard Drives Can A PC Have?
The number of hard drives you can install largely depends on how many available SATA slots you have on your motherboard.
Most motherboards have four or six SATA slots, so you can attach a maximum of six hard drives to your PC, assuming you don’t want to use a DVD writer or an SSD.
To find out the exact number of SATA slots, you can open your case and count the small L-shaped slots.
Alternatively, you can check your motherboard’s model or check the UEFI utility under integrated peripherals.
However, even if you have many SATA slots, you may not be able to use them all to install more hard drives because multiple less critical factors determine how many drives you’ll eventually have.
Factors Affecting The Number Of Hard Drives In Your PC
1. Motherboard
As mentioned, the motherboard is usually the deciding factor when it comes to the number of internal hard drives your PC can handle.
Motherboard-HDD connections come in two varieties: SATA and PATA.
A. Serial ATA (SATA)
Modern hard drives connect to the motherboard using the SATA port, a high-speed bus interface that can transfer up to 6 Gigabits of data per second.
Optical drives and SSDs also connect to your motherboard using the SATA port, taking up some of your available slots.
The SATA slot is almost the same size as a USB port, and it’s L-shaped, so you can only plug it in one way.
It uses a sturdy locking cable mechanism to prevent it from coming out or breaking off.
SATA has gone through three iterations, increasing its speed from 150 megabytes per second to 300 and 600.
There’s also a SATA express edition which allows you to mount drives directly on your motherboard’s PCI express slots and reaches speeds of up to 4 gigabytes per second.
B. Parallel ATA (PATA)
PATA connects to the motherboard using the IDE interface.
It’s an older, almost obsolete technology that allows you to connect CD/DVD drives and hard drives to your motherboard.
Older generation motherboards have two IDE slots that let you connect two drives on each cable for a total of four drives in your PC.
The PATA connection runs at 133 megabytes per second and has a capacity of 128 GB of storage per drive.
In addition to minimal speed and storage, IDE has a few crucial inconveniences.
You have to set your devices to master and slave, which wastes a lot of time on unnecessary troubleshooting.
It also uses a wide forty-lane ribbon, making cable management very complex and hampers airflow.
C. M.2
Although strictly a technology for SSDs, M.2 is worth mentioning here because it allows the SSD to be mounted directly on the motherboard, freeing up SATA slots for your hard drives.
The interface was specifically designed based on the SATA express technology.
It has significantly lower latency and higher performance through parallelization compared to a regular SATA SSD.
M.2 also uses an entirely different driver to access storage.
It’s called the Non-Volatile Memory Express (NVME) driver and is optimized for SSD access and replaces AHCI.
The new driver can handle large file transfers and multiple simultaneous requests efficiently.
AHCI can only process one queue of 32 commands at a time, whereas NVME has the capacity to handle 65,000 queues, each containing 65,000 commands.
As you can see, the difference is staggering!
The M.2 interface is also helpful for connecting wireless or Bluetooth cards, allowing you to enjoy a high-speed connection without attaching bulky cards to your USB ports.
Before purchasing an M.2 card, make sure your motherboard supports the technology.
Then only buy the version that matches your system because M.2 comes with multiple almost incompatible configurations and connector types.
Your motherboard should also accommodate the dimensions of your M.2 device.
Note: Most people confuse M.2 and NVME and use them interchangeably. However, the difference is that M.2 is the name of the physical interface that connects the disk to your motherboard, while NVME is the name of the standard used for transferring data.
2. Operating System
Although it may sound odd, operating systems have a cap on the maximum storage they can support.
That’s because your OS needs to have addresses for each sector of your hard drive to locate, read, and write the information stored in that sector—512 bytes of data.
Windows uses the Master Boot Record (MBR) mechanism with a 32-bit address space.
Therefore, the maximum number of sectors it can accommodate is 2^32*512, which comes down to 2 TB.
Moreover, the MBR only allows you to have four primary partitions, while Windows only gives you 24 letters to assign to your drive.
You can’t use all of those letters for hard drive partitions because you may need a few of them for USB sticks, optical drives, and network drives.
Fortunately, a newer address mechanism known as GPT eliminates the cap on capacity and primary partitions, but Windows 8 and earlier don’t support it.
You’ll still be limited by the number of letters in the alphabet (minus two) and the New Technology File System (NTFS).
You can always switch to Linux if you find these limits too annoying.
3. Power Supply
Hard drives don’t consume much power (between 20 to 30 watts), but they still need a power cable directly from your PSU.
You need to make sure you have enough four-pin cables coming out of your PSU to power your disks.
If you don’t have enough, you can buy a SATA power splitter cable by giving you four female power connectors.
However, cable management will be slightly more challenging, and you’ll need to make sure that you don’t overburden your PSU.
Although that might not appear unlikely, you may already be around the maximum of what your PSU can handle, depending on your setup.
When adding up the power consumption of your components, you should always account for current spikes that may send your PSU over the limit and cause it to shut down without warning.
Leave 10 to 20 percent capacity free, especially if you have one or multiple high-end graphics cards installed.
4. Space In The Case
Before you can install multiple hard drives in your case, you need to make sure there’s enough space to mount them.
You can’t simply leave the drives hanging in the air because they need proper seating to prevent bad sectors and ensure optimal operation.
Moreover, you need to have a bit of clearance between the drives as stacking them on top of each other creates unnecessary pressure on the bottom ones, and the drives negatively affect each other by vibrating.
Space is more likely to become an issue in smaller mini-towers that support ITX motherboards.
In this situation, you can consider using an external USB hard drive or an NVMe drive if your motherboard supports one.
You can also move your hardware to a larger case with adequate space.
5. Cooling
All computer hardware generates heat.
When you have more than a few components, getting rid of the heat can become a problem.
Make sure your case has proper ventilation.
If you want to install more than one extra drive, consider upgrading your cooling mechanism.
You can install more fans or buy ones with more cooling capacity.
Upgrading to water cooling is unnecessary because hard drives don’t generate nearly as much heat as GPUs and CPUs.
6. Noise
A hard drive is one of the few pieces of computer hardware with mechanical parts that cause noise.
The noise is minimal compared to the amount that heat fans generate, but it’s still noticeable, especially if you have silent fans.
If you want a completely silent operation, consider buying SSDs because they don’t have mechanical heads.
How Many Hard Drives Can A Laptop Have?
Most laptops only have one bay for a hard drive because they need to stay compact and portable.
If your laptop has an optical drive, you can replace it with a second hard drive or an SSD.
However, most newer models have eliminated the optical drive in favor of smaller designs and more portability.
However, modern laptops usually support the M.2 interface.
You can install an M.2 SSD if you need extra storage.
A cheaper option is to use an external USB 3.0 hard drive.
Although USB is typically slower than SATA and PCI express, USB 3.0’s transfer rates are high enough for most daily applications, such as productivity programs and gaming.
If you still need more storage, you can connect multiple USB hard drives to your laptop using a powered USB hub that prevents voltage drops.
Still, you should expect some performance deterioration because all the hard drives will have to share the same port to transfer data.
Another option for large-scale data storage is to run a RAID connected to a network, to which you can connect using a gigabit Ethernet connection.
How Many SSDs Can A PC Have?
SSDs use the same SATA ports to connect to your motherboard, meaning you can install as many SSDs as you have SATA slots available.
The good news is that newer generations of SSDs rely on different interfaces such as M.2.
Depending on your motherboard’s capabilities, you may be able to install additional SSDs.
We also discussed space, heat, and vibration considerations when discussing how many hard drives you can install on your PC.
Fortunately, SSDs don’t have a lot of those problems.
They take up much less space and don’t cause vibrations because they don’t have mechanical parts, meaning you can stack them on top of each other.
You also won’t have to worry much about heat dissipation as they operate best when you have temperature extremes.
Some M.2 drives come with a small heatsink that attaches to the top of the drive.
On the other hand, 2.5-inch SSD drives don’t need extra cooling because the metal casing doubles as a heatsink.
Redundant Array Of Inexpensive Disks (RAID)
You’ve probably heard about RAID to improve storage performance and reliability using multiple hard drives.
RAID comes in three main varieties for home users: RAID 0, RAID 1, and RAID 10.
RAID 0 is focused on increasing speed by increasing the number of drives.
A RAID 0 with two disks gives you double read/write speed and storage because it uses them in parallel.
However, if one of the drives dies, you’ll lose all of your data.
RAID 1 is the opposite.
It focuses on reliability by duplicating all your data on another drive.
Therefore, you’ll get the speed and capacity of one drive, but you’ll have your data in two places to prevent data loss if one of the drives fails.
RAID 1 doesn’t have any performance overhead, but it splits your effective capacity in half.
RAID 10 gives you the best of both worlds.
You’ll need at least four drives to build a RAID 10.
You’ll use two of them to double your read/write speed and the other two to double your reliability.
You can lose up to two drives in a RAID 10 array without losing any data.
Other varieties of RAID, including RAID 5 and RAID 6, are more appropriate for professional applications and data center settings.
You can also build RAIDs using SSDs, but it requires more technical knowledge, as the video below demonstrates:
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