When building or upgrading a computer, one of the most important decisions is how to configure the storage. Solid state drives (SSDs) have become the preferred option for primary storage due to their fast speeds. But should you use one large SSD or two smaller ones? There are pros and cons to each approach.
Quick Pros and Cons
Here is a quick overview of the main advantages and disadvantages of using two SSDs versus one:
Pros of Using Two SSDs:
- Increased overall storage capacity
- Faster read/write speeds from ability to access both drives simultaneously
- Added redundancy in case one drive fails
Cons of Using Two SSDs:
- Higher cost than a single large SSD
- More complex setup and file management
- May not improve real-world performance noticeably in many use cases
Pros of Using One SSD:
- Lower cost for equivalent total capacity vs. two smaller SSDs
- Simpler setup and file management
- Potentially better optimized performance from single drive
Cons of Using One SSD:
- Limited to max capacity of largest affordable single SSD
- No redundancy if drive fails
- Lower theoretical peak performance than two SSDs
Capacity Needs
One of the first considerations when deciding between one or two SSDs is your total capacity requirements. A single 1TB or 2TB SSD may be able to meet most users’ needs for primary storage. However, if you need a higher total capacity, such as 4TB or more, using two smaller SSDs can allow you to add more usable storage.
On the flip side, if you only need 500GB or less of fast SSD storage, a single drive is likely sufficient and more cost effective. Getting two 250GB SSDs instead of one 500GB SSD will cost more without providing any extra usable space.
Performance Differences
In theory, using two SSDs together in a RAID 0 configuration can provide better performance than a single SSD. The workload can be distributed across both drives simultaneously, allowing for faster read and write speeds overall.
However, in real world usage, the performance difference may not be that significant. Many activities are not heavily storage bandwidth constrained. So a single fast SSD may be able to provide adequate speeds, unless you are regularly moving large files or have a specialized high-throughput workload.
Here are some examples where using two SSDs can provide a noticeable performance advantage:
- Video editing – Faster rendering and previewing high bitrate footage
- Data analytics – Quickly processing large datasets
- Computer aided design – Working with high resolution 3D models
For general office work, web browsing, and gaming, you may not see much real world speedup from striping SSDs in RAID 0. A single SSD is often sufficient for most routine desktop usage.
Redundancy and Reliability
One clear advantage of using two SSDs instead of one is added redundancy. If one of the drives fails, your data and system will still function normally using the second drive. With a single SSD, a drive failure can lead to catastrophic data loss and system downtime.
Using a RAID 1 mirrored configuration with two SSDs can provide fault tolerance and peace of mind. However it does come at a higher cost – you need double the storage capacity for full redundancy. Another option is keeping an external backup of your important files and data.
Overall SSDs are fairly reliable, so the likelihood of a failure is low, especially if you choose a model from a reputable brand. But if uptime and data protection are critical, having a redundant SSD setup makes sense.
Ease of Setup and Management
Using two SSDs generally requires a bit more work when first installing and setting up your system. You’ll need to:
- Configure the SATA or PCIe mode and lanes for both drives
- Initialize and format both SSDs
- Set up a RAID array if desired
- Decide how to partition and manage data across both drives
With a single SSD, it’s simpler to get up and running. Just initialize, format, and partition the one drive as needed.
Ongoing file management may also be easier with one drive. You don’t have to decide where to store files and applications across multiple SSDs. Everything resides on the single large partition.
For some users, maximizing simplicity and minimizing initial setup and ongoing management overhead makes a single SSD preferable.
Cost Comparisons
In most cases, sticking with one SSD will be the more cost effective option. SSD pricing tends to drop sharply at higher capacities. A single 1TB SSD generally costs significantly less than two 500GB SSDs with the same specs.
Here’s an example cost comparison for Samsung’s popular 870 EVO SSD line:
Drive | Capacity | Price |
Samsung 870 EVO | 500GB | $69.99 |
Samsung 870 EVO | 1TB | $109.99 |
Two 870 EVO 500GB | 1TB Total | $139.98 |
As you can see, the 1TB single drive costs around $30 less than the equivalent capacity using two 500GB SSDs. This cost advantage grows even more pronounced at higher capacities. The scaling is similar across most major consumer SSD models from brands like Samsung, Crucial, Western Digital, and others.
There are some scenarios where two smaller SSDs may cost less up front. For example, you can often find good sales on smaller 120GB – 256GB drives. Combining two of those on promotion can cost less than a single 500GB+ SSD at non-discounted pricing. However you would be sacrificing usable capacity versus one large drive.
Desktop vs Laptop Use
The choice between one or two SSDs can also depend on whether this is for a desktop or laptop system. Laptops are much more physically constrained, often allowing space for just one SSD. Trying to add a second laptop SSD will either require replacing the optical drive or specialized adapters.
For desktops, adding a second SSD is an easy upgrade. There are typically multiple drive bays and SATA ports to work with. RAID configurations are also more practical on desktops.
So for laptop builds, sticking with one SSD is generally the simplest and most cost effective approach. But for desktops, using two SSDs in RAID can be a viable option if your needs demand increased capacity, redundancy, or peak performance.
NVMe vs SATA SSDs
Another consideration is whether to go with NVMe or SATA SSDs. NVMe drives connect via PCIe directly to the CPU and system bus. This allows for much higher sequential read/write speeds compared to SATA SSDs.
In order to take full advantage of NVMe drive speeds, using two in RAID 0 makes more sense. The SATA interface itself is limited to around 550 MB/s. But a pair of PCIe 3.0 x4 NVMe SSDs in RAID can reach sequential read/write speeds of 6,000 MB/s or more.
If going with SATA SSDs, the interface speed ceiling makes the benefits of RAID more modest. Still a dual SATA RAID 0 setup can provide somewhat improved response times and bandwidth during demanding multitasking.
For professional media production, engineering, scientific work, or other storage intensive tasks, combining two NVMe SSDs provides the fastest SSD RAID performance. But for lighter workloads, even a single SATA SSD is sufficient.
IDE/AHCI Considerations
If building a new system, modern motherboards typically support SATA disks in AHCI mode. This allows the SATA controller to optimize disk access and use features like Native Command Queuing.
In older systems limited to IDE mode, it’s better to stick with a single SSD. IDE can’t take advantage of the parallelism of multiple SSDs in RAID configurations. AHCI mode must be used on the SATA controller to see any performance benefits from RAID.
PCIe Lanes
When installing multiple NVMe SSDs, you’ll want to make sure your motherboard has enough PCIe lanes to avoid bottlenecking the drives. Many consumer boards only have one x4 PCIe 3.0 slot, with additional M.2 slots running in x2 mode.
For optimal NVMe RAID performance, choose a high end desktop motherboard with multiple full x4 PCIe slots. Or use an add-in PCIe expansion card to add more lanes. Without adequate PCIe bandwidth, NVMe SSDs can be choked and limited to speeds below their rated specs.
TRIM and SSD Optimization
Enabling TRIM is important to maintain continued performance on SSDs as data is rewritten over time. TRIM commands help reset and purge invalid data blocks.
Unfortunately TRIM and other SSD optimizations are typically not supported when using RAID. The RAID controller handles lower level block management rather than the SSD firmware.
This can lead to modestly slower write performance on SSD RAID arrays as they fill up over time. For general home and office use this may not be noticeable. But for workloads with sustained writes, a single SSD with TRIM may offer better long term performance.
Drive Failure and Data Recovery
One double edged sword of using two SSDs in RAID 0 for increased performance is the very real risk of data loss. Because data is striped across both disks with a portion on each drive, failure of either SSD will result in total data loss.
Recovering from a single drive failure in RAID 0 requires sending both SSDs out for professional data recovery. This is an expensive process with no guarantee of success.
With a single SSD, if it fails you can try simpler recovery methods yourself. Or if the drive hardware itself is still ok, specialized data recovery firms can often retrieve data with high success rates.
Regular external backups are wise to hedge against failure regardless of RAID or single drive configurations. But RAID 0 does multiply the points of failure.
Hybrid SSD and HDD Combinations
Another option instead of using two SSDs is to pair a single SSD with a high capacity traditional hard disk drive (HDD). An SSD + HDD combo allows you to balance speed and storage capacity at a lower cost than an all SSD setup.
For example you could install Windows and frequently used applications on a 500GB SSD for the performance benefits. And then store media files and documents on a 2TB HDD.
The total storage capacity is larger than two 500GB SSDs, at a lower cost than one 2.5TB SSD. And you still get the SSD speedup for system files and daily active programs.
If going the SSD + HDD route, it’s best to use two separate standalone physical drives. Trying to combine an SSD and HDD in a single hybrid drive typically doesn’t work as well. The firmware often struggles optimizing which data should reside on the faster SSD section.
Conclusion
There are plenty of good reasons to consider using two SSDs – increased capacity, better speed, and redundancy prime among them. For power users with demanding storage needs, a dual SSD setup can provide real benefits.
But in many common scenarios, choosing one larger SSD ends up being the smarter move. The simplicity, lower cost, and minimal performance sacrifice will suit most general users just fine.
Here are some final tips to help decide between one versus two SSDs:
- Two SSDs make more sense for higher capacity needs of 2TB or more.
- Consider RAID 0 when regularly working with large files or high throughput applications.
- Weigh the tradeoffs of redundancy/reliability versus cost and simplicity.
- Make sure your motherboard has enough SATA ports and PCIe lanes.
- Desktops can better utilize multiple SSDs compared to space constrained laptops.
The choice depends heavily on your budget, usage requirements, and tolerance for complexity. For most home and office users doing routine productivity work, web browsing, and gaming, a single fast SSD delivers excellent performance. But if regularly pushing high bandwidth loads, the added power of RAID 0 can become appealing.