What are the differences between an HDD (Hard Disk Drive) and an SSD (Solid State Drive)? Why are SSDs supposed to give you faster speed?
In: Technology
A Hard Disk Drive (HDD) is like a solid plate that is spinning – there are faster and slower ones – and it has mechanical heads for reading and writing information. These are the traditional permanent storage devices on computers. They can be slower because of how it reads and writes data.
Solid State Drives (SSD) are basically like a memory card you’d plug into your phone or camera – there are no moving parts and it can read and write information much more quickly.
HDD is like trying to get information off the Wheel Of Fortune while a SSD is more like playing BINGO.
The wheel has to spin to get to the spot the data is at.
The SSD just ask for the info and the spot says it’s here.
A couples of terms and definitions first. And a simplified answer.
Hdd – data is stored on disks that spin and theres an arm that moves to reads/writes from locations. Data that is very spread out has a large impact on performance.
Ssd – data is stored in cells and there is a path to each cell. Some cells shared the same wire so only one cell on that bus can be active at any one time. Data that is spread out has a moderate impact on performance.
Seek time – time between request of data and the data being returned. Ssds are like <0.2ms. Hdds are like 5-20+ ms.
Throughout or transfer rate – sustained read or write speeds. Hdds are capped around 100MB/s. Ssds go up to a few GB/s. But a low end ssd is typically <500MB/s.
Since responsiveness is more noticable than raw transfer rate you can see the ssd is much more responsive. However if you are constantly transfering large files than throughput helps too.
But any cheap ssd will make your computer seem faster/responsive compared to a hdd that’s chugging along.
HDD and SSD have about the same speed when reading a single large file, like when you’re loading a video. SSD is by far faster when you’re reading from many different small files, or try to do many different things at once.
The reason for the speed difference is that HDD reads a spinning platter using a Head, like a record player. It takes time to lift the head and moving it to another location, so anytime that HDD reads from files that are not right next to each other, it takes extra amount of time.
On the other hand, SSD uses Flash, which is the same stuff that’s in the USB thumb drives, but SSD have a lot of Flash chips. First of all, Flash chips don’t have that Head problem – if you want to read from a different place, you just go read it. Also, SSD reads from all of those Flash chips all at once. That’s how SSD’s can be so fast.
HDD is like a CD. It has to spin to work.
SDD is like a USB stick. No movement required.
SDD is just much more enhanced than an HDD because it is newer.
Data on a HDD is like having a factory full of stuff, and you tell an employee “you there, go take a photo of that thing from Row 4, shelf 5, and then send it to me, oh and also get me the thing from Row 2, shelf 3.” So the employee has to run over to the first thing, grab the information and send it over to the boss, then he runs over to the next thing the boss wanted, and then send that over.
The bottleneck in terms of speed is how fast the little employee can run from the starting point to point A, and then point B, which could be at complete opposite ends of the factory. Things get worse with fragmentation where a single file is split into several chunks. Now the task of requesting file A involves multiple stops and just adds even more to travel time because Bob decided it’d be a great idea to scatter the pages of document A everywhere.
Also hdds at their peek performance are limited to how fast the plates are spinning. Imagine a record player, if you want a copy of the song, you have to wait for the stylus to read the song information slowly as the record spins, you are limited to how fast that record is designed to spin.
With SSDs, all the data is in a single spot, and can be accessed instantly with zero moving parts. The boss requests a file, and it is immediately given. Even if it’s in 100 fragments it doesn’t matter, because there is no travel time anymore between finding the pieces and how fast it can read that information. It is a significantly more optimal process so the speed goes waaay up.
SSD is much faster compared to HDD. My desktop with a HDD will take 5 minutes to load up properly, where my laptop with an SSD loads up in about 10 seconds.
A hard disc drive has a spinning metal or glass platter inside, coated with a magnetic material. They work on the same basic technology as cassette tapes and floppy discs. A read head moves over the disk and whether a particle is magnetized or not represents a binary 1 or 0. The head can also write data by magnetizing the surface. Hard drives are slow, as they have to physically move something to find data. Platters can also only spin so fast. But they have a high capacity. Making them ideal for storing a lot of data cheaply.
SSDs use Flash memory, which uses tiny transistors to store data, very similar to how computer RAM works. Unlike RAM, they are non-volatile, which means they can retain stored data without receiving power. It does this using something called a floating-gate. This is a semiconductor material that can be charged, and will retain that charge, over very long periods of time. Flash is considerably faster, but also costs more per gigabyte than hard drives. The floating gates also lose their ability to hold a charge with repeated writes. Solid state drives are ideal for applications that require fast reads. It’s less useful for applications that require a lot of continuous writes (like security cameras or DVRs), or for bulk data storage.
The “sold state” comes from the fact that Flash has no moving parts.
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