What is an SSD?
Matthew Connatser
2 days ago
Storage is one of the few parts of a computer that gets a complete and total makeover every now and then. We started with tape, moved to floppy disks, then to hard drives, and now solid state drives, or SSDs. The SSD is the latest in a chain of very different storage technologies, though it hasn't totally replaced its predecessor (yet, anyway). Here's the story of the SSD and how it has gradually become the primary storage device for computers everywhere.
Small, light, and efficient
The biggest innovation of the SSD is that it's 100% digital, meaning it uses absolutely no moving or mechanical parts in order to operate. Mainstream storage mediums that preceded the SSD, like tape, floppy disks, DVDs, and hard drives (or HDDs), were all partially mechanical or analog. Being 100% digital allows SSDs to be very small, ranging from the size of your hand to the size of your finger. SSDs are much lighter and more efficient than HDDs, which have been (mostly) succeeded by SSDs.
What makes the SSD possible is NAND flash memory, a tiny silicon chip the size of the tip of your finger, and a single chip can store up to two terabytes at the time of writing (cheaper devices will use lower capacity chips though). In many respects, NAND flash is very similar to RAM, which is also a chip that can store lots of data and are sometimes used in SSDs to make them even faster. There are three key differences between NAND flash and RAM though: RAM is much faster, NAND chips have higher capacities for a lower price, and NAND doesn't require constant power in order to retain data.
Although flash memory is key to the SSD, not all devices that use flash memory are considered SSDs, such as USB flash drives and SD cards. An SSD is typically a high-performance implementation of flash memory that can either be installed into a computer directly or in an external enclosure that connects to a computer. The only real difference between a USB flash drive and an external SSD is that the SSD might be faster and higher capacity.
The different kinds of data interfaces and memory types for SSDs
Although all SSDs use flash memory, there can be significant differences between different models. The two key specifications to look out for are the data interface and the memory type, which have a significant impact on both performance and compatibility.
The data interface of an SSD is something you can't ignore even if you're not an enthusiast, because it's how your SSD connects to your computer. Generally speaking, there are three main ways to connect an SSD to a device: PCIe, SATA, and USB. Of the three, PCIe offers the fastest transfer speeds, and newer versions of PCIe enable SSDs to hit even higher speeds. Although SATA is significantly slower than PCIe, it's not cripplingly slow and is suitable for older models. On even the latest versions of USB however, SSDs can be pretty slow because the USB interface just isn't optimal for SSDs.
These interfaces aren't just digital, but also physical. PCIe can be used through either one of the x16 slots on the motherboard or via an M.2 slot compatible with tiny NVMe SSDs. SATA on the other hand is usually used for 2.5 inch SSDs, though some SATA SSDs are in the M.2 form factor and some M.2 slots are SATA compatible. While modern desktops are compatible with most (if not all) types of PCIe and SATA SSDs, most modern laptops only use NVMe SSDs.
While there are many aspects to flash memory that determines key characteristics, one of the most important specifications is the size of cells, which are the things that store the individual ones and zeroes that make up data in flash memory. Most flash memory stores one, two, three, or four bits per cell, and while bigger usually means better, in this case it's not always true. Cells with less bits are faster and have more endurance, while cells with more bits can store data more densely.
Single-level cell (or SLC) memory just stores one bit, and it's the fastest and most durable kind of flash. However, its low data density means this kind of memory is the most expensive. Multi-level cell (or MLC) memory has two bits per cell, triple-level cell (or QLC) has three bits, and quad-level cell (or QLC) has four bits. Today, QLC is very popular for cheap drives like Solidigm's P41 Plus, while TLC is sufficient enough for high-end drives like Samsung's 990 Pro. SLC and MLC are mostly for professional and data center computers due to their high cost and overkill performance for everyone else.
Why the SSD hasn't totally killed the HDD yet
After all of this, you might be wondering why the hard drive is still around. SSDs are super modern, orders of magnitude faster, and are far smaller. While all of these things have helped SSDs mostly take over the storage market, there are a few reasons why the SSD hasn't killed the HDD like the HDD killed the floppy disk.
One of the biggest reasons (and perhaps the main reason) is that HDDs are much cheaper than SSDs. At the time of writing, SSDs are hitting the lowest prices we've ever seen, but a fairly midrange 2TB SSD still costs around $70, while 2TB HDDs can be found for $40 to $50. If you're buying lots of storage, that difference adds up very quickly. Also, it's highly likely that SSDs won't be this cheap for this long, as manufacturers are reducing production to escape these rock bottom prices.
HDDs also have another storage related advantage: size. The biggest HDDs can store 22TB of data, and although super high-end SSDs for data centers can store as much as 100TB, the biggest consumer SSDs only hit 15.3TB. But even then, 15.3TB SSDs aren't very common and if you want a high capacity SSD, you'll have to settle for a more mainstream 8TB model. Of course, these SSDs are physically smaller than HDDs, but most motherboards have more SATA ports than M.2 and PCIe slots, meaning you can store more data using HDDs.
What ultimately makes the HDD still very usable after all these years is the fact that speed isn't everything. Sure, for your operating system, games, and other software, using an SSD is much better than using an HDD, but long term data storage doesn't require high speed. When you consider HDDs can get more storage at a lower cost than SSDs, the HDD is the obvious choice for storing data that you don't access all the time. The HDD will only be completely replaced when SSDs can offer equal bang for buck when it comes to capacity.
Matthew Connatser
2 days ago
Storage is one of the few parts of a computer that gets a complete and total makeover every now and then. We started with tape, moved to floppy disks, then to hard drives, and now solid state drives, or SSDs. The SSD is the latest in a chain of very different storage technologies, though it hasn't totally replaced its predecessor (yet, anyway). Here's the story of the SSD and how it has gradually become the primary storage device for computers everywhere.
Small, light, and efficient
The biggest innovation of the SSD is that it's 100% digital, meaning it uses absolutely no moving or mechanical parts in order to operate. Mainstream storage mediums that preceded the SSD, like tape, floppy disks, DVDs, and hard drives (or HDDs), were all partially mechanical or analog. Being 100% digital allows SSDs to be very small, ranging from the size of your hand to the size of your finger. SSDs are much lighter and more efficient than HDDs, which have been (mostly) succeeded by SSDs.
What makes the SSD possible is NAND flash memory, a tiny silicon chip the size of the tip of your finger, and a single chip can store up to two terabytes at the time of writing (cheaper devices will use lower capacity chips though). In many respects, NAND flash is very similar to RAM, which is also a chip that can store lots of data and are sometimes used in SSDs to make them even faster. There are three key differences between NAND flash and RAM though: RAM is much faster, NAND chips have higher capacities for a lower price, and NAND doesn't require constant power in order to retain data.
Although flash memory is key to the SSD, not all devices that use flash memory are considered SSDs, such as USB flash drives and SD cards. An SSD is typically a high-performance implementation of flash memory that can either be installed into a computer directly or in an external enclosure that connects to a computer. The only real difference between a USB flash drive and an external SSD is that the SSD might be faster and higher capacity.
The different kinds of data interfaces and memory types for SSDs
Although all SSDs use flash memory, there can be significant differences between different models. The two key specifications to look out for are the data interface and the memory type, which have a significant impact on both performance and compatibility.
The data interface of an SSD is something you can't ignore even if you're not an enthusiast, because it's how your SSD connects to your computer. Generally speaking, there are three main ways to connect an SSD to a device: PCIe, SATA, and USB. Of the three, PCIe offers the fastest transfer speeds, and newer versions of PCIe enable SSDs to hit even higher speeds. Although SATA is significantly slower than PCIe, it's not cripplingly slow and is suitable for older models. On even the latest versions of USB however, SSDs can be pretty slow because the USB interface just isn't optimal for SSDs.
These interfaces aren't just digital, but also physical. PCIe can be used through either one of the x16 slots on the motherboard or via an M.2 slot compatible with tiny NVMe SSDs. SATA on the other hand is usually used for 2.5 inch SSDs, though some SATA SSDs are in the M.2 form factor and some M.2 slots are SATA compatible. While modern desktops are compatible with most (if not all) types of PCIe and SATA SSDs, most modern laptops only use NVMe SSDs.
While there are many aspects to flash memory that determines key characteristics, one of the most important specifications is the size of cells, which are the things that store the individual ones and zeroes that make up data in flash memory. Most flash memory stores one, two, three, or four bits per cell, and while bigger usually means better, in this case it's not always true. Cells with less bits are faster and have more endurance, while cells with more bits can store data more densely.
Single-level cell (or SLC) memory just stores one bit, and it's the fastest and most durable kind of flash. However, its low data density means this kind of memory is the most expensive. Multi-level cell (or MLC) memory has two bits per cell, triple-level cell (or QLC) has three bits, and quad-level cell (or QLC) has four bits. Today, QLC is very popular for cheap drives like Solidigm's P41 Plus, while TLC is sufficient enough for high-end drives like Samsung's 990 Pro. SLC and MLC are mostly for professional and data center computers due to their high cost and overkill performance for everyone else.
Why the SSD hasn't totally killed the HDD yet
After all of this, you might be wondering why the hard drive is still around. SSDs are super modern, orders of magnitude faster, and are far smaller. While all of these things have helped SSDs mostly take over the storage market, there are a few reasons why the SSD hasn't killed the HDD like the HDD killed the floppy disk.
One of the biggest reasons (and perhaps the main reason) is that HDDs are much cheaper than SSDs. At the time of writing, SSDs are hitting the lowest prices we've ever seen, but a fairly midrange 2TB SSD still costs around $70, while 2TB HDDs can be found for $40 to $50. If you're buying lots of storage, that difference adds up very quickly. Also, it's highly likely that SSDs won't be this cheap for this long, as manufacturers are reducing production to escape these rock bottom prices.
HDDs also have another storage related advantage: size. The biggest HDDs can store 22TB of data, and although super high-end SSDs for data centers can store as much as 100TB, the biggest consumer SSDs only hit 15.3TB. But even then, 15.3TB SSDs aren't very common and if you want a high capacity SSD, you'll have to settle for a more mainstream 8TB model. Of course, these SSDs are physically smaller than HDDs, but most motherboards have more SATA ports than M.2 and PCIe slots, meaning you can store more data using HDDs.
What ultimately makes the HDD still very usable after all these years is the fact that speed isn't everything. Sure, for your operating system, games, and other software, using an SSD is much better than using an HDD, but long term data storage doesn't require high speed. When you consider HDDs can get more storage at a lower cost than SSDs, the HDD is the obvious choice for storing data that you don't access all the time. The HDD will only be completely replaced when SSDs can offer equal bang for buck when it comes to capacity.
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Summary
Title: Understanding Solid State Drives (SSDs)
Topic: SSD, NAND flash memory
Key Information:
- SSDs are a digital storage technology that have gradually become the primary storage device for computers.
- They operate without any moving or mechanical parts, unlike previous storage
Topic: SSD, NAND flash memory
Key Information:
- SSDs are a digital storage technology that have gradually become the primary storage device for computers.
- They operate without any moving or mechanical parts, unlike previous storage