Solid state drives (SSDs) have become a popular storage solution for computers and other devices due to their faster speeds and improved reliability compared to traditional hard disk drives (HDDs). When purchasing an SSD, one of the key factors to consider is the drive’s storage capacity or size.
What are the common SSD sizes available?
SSD sizes generally range from 120GB to 4TB for consumer drives. Some of the most common sizes are:
- 120GB
- 240GB
- 480GB
- 500GB
- 1TB
- 2TB
Larger enterprise and data center SSDs may go up to 8TB or even 16TB. Additionally, smaller SSDs down to 32GB or 64GB are available for tablets and other compact devices.
How do SSD sizes compare to HDD sizes?
Consumer HDD capacities typically start at 500GB and go up to 10TB+. Enterprise HDDs can be as large as 16TB. So while the very largest HDDs still exceed the capacities of even the biggest SSDs, there is significant overlap in the common size ranges. A 1TB SSD would be considered a fairly typical capacity, while 1TB HDDs are also very common.
Why are SSD capacities generally lower than HDDs currently?
SSD capacities continue to increase each year, but remain lower than HDDs primarily because of cost. High capacity NAND flash memory remains more expensive than mechanical hard drive technology. However, the gap is narrowing over time.
What factors affect SSD prices per GB?
Some key factors that influence the cost per GB of SSD storage include:
- NAND flash type – SLC, MLC, TLC, QLC. SLC is most expensive while QLC is cheapest.
- Drive form factor – 2.5″ vs M.2 vs U.2 etc.
- Interface – SATA, PCIe NVMe, etc.
- Controller technology
- Brand name and model – Major brands like Samsung tend to command higher prices
- Retailer pricing model
Higher capacity SSDs generally have a lower cost per GB. However, lower capacity drives can have a better price if they use cheaper QLC NAND or more basic controller hardware.
What are typical uses cases for varying SSD sizes?
Here are some examples of how SSD size capacities are commonly matched to different uses:
- 120-256GB – Boot drive for basic computing, lightweight laptops
- 480GB-1TB – Primary drive for mid-range laptops and desktops
- 1-2TB – Enthusiast primary drive, gaming rigs, workstations
- 4TB+ – Professional workstations, servers
For a boot drive, 120GB provides room for the OS and a few key programs, while 240+ GB offers more flexibility. For general computing and gaming, 480GB/500GB is a common starting point today. Heavy users may want 1TB or more for primary storage.
How does SSD endurance change with different sizes?
Endurance is measured in drive writes per day (DWPD) or total terabytes written (TBW) over the lifespan of an SSD. How does endurance scale across differently sized drives?
- DWPD tends to be similar across a product line regardless of capacity. For example, 0.3 DWPD for both a 256GB and 1TB model SSD.
- TBW ratings increase with higher capacities. A 1TB drive will be rated for a higher total TBW than a 128GB drive of the same model line and NAND type. For example, 400TBW vs 100TBW.
The reason TBW increases with capacity is because the writes are distributed across more NAND flash memory chips. Each chip has a fixed endurance spec based on the type of NAND (SLC/MLC/TLC/QLC).
Example SSD TBW Ratings by Capacity
| SSD Model | 128GB TBW | 256GB TBW | 512GB TBW | 1TB TBW |
| Samsung 870 EVO SATA | 150TBW | 300TBW | 600TBW | 1200TBW |
| WD Blue SN550 NVMe | 100TBW | 200TBW | 400TBW | 600TBW |
How does sequential read/write speed scale with SSD size?
Larger capacity SSDs generally have faster maximum sequential read/write speeds, which are measured in MB/s. This is because higher capacities have more NAND flash memory chips that can be read/written to simultaneously. Below is an example comparing speeds of 512GB vs 2TB models for a particular SSD:
| 512GB Sequential Read | 512GB Sequential Write | 2TB Sequential Read | 2TB Sequential Write | |
| Samsung 870 EVO SATA | 560 MB/s | 530 MB/s | 560 MB/s | 530 MB/s |
In this SATA interface example, the sequential speeds are identical. With an NVMe drive the difference would be more pronounced. However, at the same capacity Sequential read/write speeds are limited by the drive interface (SATA vs NVMe), not necessarily total size.
How does random read/write performance scale with SSD size?
Random read/write speeds are measured in IOPS (input/output operations per second) and are important for tasks like booting an OS, launching programs, and multitasking. For a given SSD model, random IOPS performance tends to be very similar across capacities due to the following factors:
- Random reads/writes target small blocks of data across the flash memory and do not fully saturate the controller or interfaces.
- Controller and interface bandwidth become the limiting factor, not total NAND chips.
- Garbage collection routines run on all capacities and can limit random IOPS.
For example, the Samsung 870 EVO SATA SSD above has virtually identical random read/write specs for 512GB and 2TB models of 98K/88K IOPS respectively. So random IOPS cannot be improved substantially just by choosing a larger drive capacity.
When does it make sense to choose a higher capacity SSD?
The main reasons to choose a higher capacity SSD are:
- You need more storage space for apps, games, files, etc.
- To take advantage of higher sequential read/write speeds that can benefit large file transfers.
- For increased endurance (TBW) that comes with more NAND to write to.
But if your usage is mostly light computing and OS/app boots, a lower capacity SSD may be perfectly sufficient and more economical. In many cases, adding a secondary HDD for mass storage can complement a more moderately sized SSD boot drive.
What are typical form factors for varying SSD capacities?
Smaller SSD capacities naturally lend themselves to smaller physical drive sizes with compact form factors. Here are some examples:
- 32GB-128GB – M.2 2230 or 2242 for laptops and tablets
- 128GB-512GB – M.2 2280 for ultrabooks and PCs
- 256GB-2TB – 2.5″ drive form factor, 7mm for laptops, 9.5mm for desktops
- 1TB-4TB – 2.5″ drive form factor, 15mm for high capacity enterprise SSDs
M.2 cards allow for capacities up to 2TB currently, while the traditional 2.5″ SSD form factor can support up to multi-TB capacities. Enterprise data center SSDs may use more exotic interfaces and form factors like U.2.
What is overprovisioning and how does it relate to SSD capacity?
Overprovisioning refers to the difference between the physical capacity of the NAND flash memory chips on a drive and the usable capacity presented to the operating system. For example, a 512GB SSD may contain 512Gb (64GB) of NAND flash per memory chip, but 8 chips for a total raw capacity of 512GB. After firmware optimizations, only 480GB ends up visible to the OS.
Overprovisioning improves performance and endurance. The extra hidden space allows the controller to better spread out writes and optimize garbage collection routines. Typically 7-28% of raw capacity is overprovisioned. Higher capacity SSDs have more room to overprovision – a 512GB drive can reserve more unused space than a 128GB model.
How can I determine the physical versus usable capacity?
SSD hardware specs may list both usable and raw NAND flash capacities. Alternately, software tools like Hard Disk Sentinel can show the difference between physical memory present and visible capacity. A 512GB SSD displaying 480GB capacity would indicate 7% overprovisioning.
Higher overprovisioning ratios result in better performance and endurance. But they reduce the usable space. Most consumers prefer to optimize for maximal usable capacity, while enterprise SSDs emphasize performance.
What kind of interfaces are typical for SSDs? Do capacities affect interface options?
Common SSD interfaces include:
- SATA – Used for 2.5″ SSD form factors. SATA limits speeds to around 550MB/s.
- PCIe NVMe – Much faster interface used for M.2 SSDs. NVMe drives can reach over 3,000MB/s.
- U.2 – Enterprise SSD interface supporting PCIe NVMe for data centers. Allows hot swapping.
For SATA, capacities make little difference – a 2TB drive won’t exceed 550MB/s. But for NVMe, higher capacity SSDs with more NAND chips can better utilize interfaces like PCIe Gen3 x4 (~3,500MB/s) or upcoming PCIe Gen4. Overall, capacities don’t limit interface compatibility if the physical drive form factor is correct.
What are typical SSD performance ranges by interface and capacity?
| SATA Max Speed | NVMe PCIe 3.0 x4 Speed | |
| 128-256GB | 500MB/s Seq. Read | 3,000MB/s Seq. Read |
| 512GB-1TB | 550MB/s Seq. Read | 3,200MB/s Seq. Read |
| 2TB+ | 550MB/s Seq. Read | 3,500MB/s Seq. Read |
For reference, here are typical sequential read speeds for varying capacities over SATA vs PCIe NVMe interfaces. At a given capacity, NVMe offers nearly 6X higher speed than SATA. Within NVMe, larger drives can better saturate interface bandwidth.
How do M.2 SSD capacities affect motherboard compatibility?
M.2 SSD maximum capacities are determined by PCIe lanes provided by the motherboard slot:
- M.2 PCIe 3.0 x2 – Up to 2TB
- M.2 PCIe 3.0 x4 – Up to 4TB
On many mainstream consumer motherboards, only smaller PCIe 3.0 x2 M.2 slots are available, limiting capacities to 2TB even if the SSD itself supports more. Check your motherboard M.2 slot specs to ensure your desired SSD will function properly.
Do capacities affect SSD power consumption?
Higher capacity SSDs draw marginally more power at peak load since they have more NAND chips. However, the differences are generally minimal. For example:
- Samsung 860 EVO 500GB – Max 3.3W read, 4.0W write
- Samsung 860 EVO 2TB – Max 3.8W read, 4.3W write
At idle, there is often no difference in power draw between capacities of the same model. Overall, power consumption should not be a major factor in choosing SSD capacity.
How does SSD controller cache scale with drive size?
The controller contains DRAM cache memory which functions as a read/write buffer. Larger cache improves performance. Controller cache capacity does not always increase with SSD size, but examples include:
- WD Blue SN570 250GB – 256MB cache
- WD Blue SN570 1TB – 1GB cache
Cache may stay the same when upgrading within a product line, like 256GB to 512GB. But doubling capacity sometimes doubles cache – so capacity can potentially impact performance.
Should I choose the largest capacity SSD I can afford?
The ideal SSD capacity depends on your specific needs and budget. Larger drives have pros and cons:
Pros:
- More storage space for apps and files
- Higher sequential read/write speeds
- Increased endurance ratings (TBW)
Cons:
- Higher upfront cost per GB
- Diminishing returns on performance past a certain point
If your main priority is maximizing capacity within a set budget, choosing a larger SSD may not be the best value. In many cases a combination of moderate SSD capacity supplemented by a secondary hard drive can offer a good balance of speed, storage space, and affordability.
Conclusion
SSD capacities span from tiny 32GB drives to massive 16TB models. Understanding typical size ranges, use cases, and how capacity impacts other aspects of SSD performance helps ensure you choose the right drive. While larger SSDs have benefits under certain workloads, restraint on capacity is often wise to keep costs reasonable for the average consumer.