What are Difference Between SSD and HDD hard disk?

SSD and HDD hard disk

we are going to compare the two types of storage drives which are commonly used to store the data permanently in desktop and the laptops. Now, conventionally these hard disk drives are used as a storage solution in desktop and the laptop. And these hard disk drives are in use for more than two decades. But in recent years, the SSDs or solid state drives are gaining the popularity because of its speed and the performance. So, in this video, let's compare these two drives in aspects like speed and performance, working principle, cost and the storage capacity and many other aspects. So, first of all, let's compare these two drives in terms of their speed and the performance. Now, the technology of hard disk drive has improved significantly over the past two decades. And the data density of this drive has increased tremendously. But the speed of hard disk drive hasn't increased at the same pace. Typically, the access time of today's hard drive is in the range of few ms. And the sequential read or write speed is typically around 100 MBPS. If you are thinking the speed of the hard drive is not bad then let me tell you that the access time of RAM and the cache memory which is used in the computer is in the range of nanoseconds. Which is significantly less than the access time of these hard drives. So, even if you have very high-end CPU, coupled with graphics card and RAM, still you will not be able to extract the best performance out of that system if you are stuck with the slow hard disk drives. Now, here don't get me wrong. 

SSD and HDD hard disk

The with top CPU and GPUs, the performance of the system will definitely increase. But because of the limitation of the hard drive, the system boot time and the opening of the applications will not be that fast. While on the other end, if we talk about the SSDs, they are much faster and have access time typically in the range of microseconds. And typical sequential read and write speed is in the range of 400 to 500 MBPS. And in fact, even it is possible to achieve the sequential read and write speed in the range of Giga Bytes per second using this SSDs. So, now let's look into the internal structure of these drives and let's find out why SSDs are so fast and hard disk drives are relatively slow in comparison to these SSDs. So, if you look inside the hard disk drive, it consists of rotating disk, which is commonly known as the platers. So, these platters rotate at the typical speed of 5400 or 7200 RPM in laptops. And it can go up to 10000 RPM in desktop computers. And in some enterprise hard disk, the speed can go up to 15000 RPM. So, in these hard disk drive, the data is stored magnetically on these platters using the head. And typically the data is stored in this hard disk drive in form of tracks and the sectors. Now, as it involves the mechanically moving parts, there is a limitation on the speed at which the data can be accessed or written on these hard disk drives. On the other end, the SSDs are designed using the flash memory. And to be precise if I say, they are designed using the NAND flash memory. So, as these SSDs are designed using the NAND flash memory, and does not have any moving part, they have very fast access time and very low latencies. So, apart from the flash memory, the SSD also contains the microcontroller and the small 

SSD and HDD hard disk

cache memory. So, using the microcontroller, the flash memory cells can be accessed or programmed. And using the cache memory it is possible to store the incoming and the outgoing data temporarily, so now let's compare the two drives in terms of the form factor. So, today's hard disk drives are typically available in two form factors. For desktop, it is available in 3.5-inch form factor, while for a laptop it is available in 2.5-inch form factor. On the other end, the SSDs are available in many form factors. The most common is the 2.5-inch form factor, where these drives can be used or replaced in place of hard disk drives. Apart from these, the mSATA and the M.2 SSDs are available in very small form factors. And they are used in ultrabooks and tablets. Alright, so now let's compare these two drives in terms of the system interface. So, the system interface defines how these drives are connected or interfaced with the system. So, the earlier hard drives were connected to the system using the PATA interface. Which is known as the parallel ATA. But today's hard drives are connected to the system using the SATA interface. While enterprise hard drives are connected to the system using the SAS protocol. On the other end, if we talk about the Solid State Drives, mSATA and SATA hard drives are 

SSD and HDD hard disk

connected to the system using SATA interface. While M.2 SSD can communicate with the system using either SATA or PCI express bus. So, now if we compare these drives in terms of the storage capacity then for the hard disk drive, 1TB capacity is most common in desktops and laptops. But for desktops, even 10 Tery Bytes of hard drives are commonly available in markets. And if we talk about the SSDs, then as of now the SSDs are available from 120GB up to 4TB. For laptops typically, it is available from 120 GB up to 1TB. While for the desktop it is available up to 4TB. But if we talk about the cost, then these SSDs are much costlier than the hard disk drives. As of now the cost per GigaBytes for SSD is almost 3 to 4 times the hard disk drive cost. But as the demand of SSD is growing, the cost is also reducing. And perhaps one day, it will become as cheap as the today's hard disk drives. So, now let's compare these drives in terms of the power consumption and the reliability. So, as these hard disk drives inc=volves the mechanical moving part the power consumption of this drive is more than the SSDs. And they are more prone to the damages in case of shock and the vibrations. So, now finally let's compare them in terms of the data durability. So, in terms of the data durability, hard drives are more durable and data can be stored for longer times without being powered up. Apart from that as we have seen, these SSDs are designed using the flash memory. And because of that the number of programs or erase cycles that can be performed on these SSDs are limited. Typically, it used to be in the range of 10000 to 100000. 

And depends upon the quality of the controller as well as the internal structure of the flash memory. Now, some manufacturers also provide the endurance rating for these SSDs. And typically it is defined by the term drive writes per day. It means that the number of times the user capacity of the drive can be written per day over the warranty period. For example, if you have 100GB of a drive, which has DWPD rating of 10, it means that 1000GB or 1TB of data can be written into this drive every day over the warranty period. So, basically, this term defines the endurance rating for the SSDs. But for most of the users, this rating is quite significant. And even if someone uses this SSD quite extensively then also it will work reliably over more than 5 years. So, overall SSDs have many advantages over the hard disk drives. But as of now, these SSDs are quite costlier than the hard disk drives. So, if someone is looking for big storage pull, with the reasonable cost then he can go for the hard disk drive. While on the other end, if someone wants very fast performance and willing to pay extra money for that performance then one can go for the SSDs.