在购买新笔记本电脑时，您可能已经看到人们争论带HDD 的设备还是带 SSD 的设备更好(HDD is better or one with an SSD)。这里的硬盘(HDD)是什么？我们都知道硬盘驱动器。它是一种大容量存储设备，通常用于个人电脑、笔记本电脑。它存储操作系统和其他应用程序。SSD或固态(Solid-State)驱动器是传统硬盘驱动器(Hard Disk Drive)的更新替代品。它是最近才进入市场的，而不是几年来一直是主要大容量存储设备的硬盘驱动器。
尽管它们的功能类似于硬盘驱动器，但它们的构造和工作方式都不像HDD(HDDs)。这些差异使SSD(SSDs)独一无二，并为该设备提供了一些优于硬盘的优势。让我们更多地了解固态驱动器、它们的架构、功能等等。(Let us know more about Solid-State Drives, their architecture, functioning, and much more.)
什么是固态硬盘 (SSD)？
我们知道内存可以有两种类型——易失性和非易失性(volatile and non-volatile)。SSD是一种非易失性存储设备。这意味着即使在电源停止后，存储在SSD上的数据也会保留。(SSD)由于(Due)其架构（它们由闪存控制器和NAND闪存芯片组成），固态驱动器也称为闪存驱动器或固态磁盘。
SSD——简史(SSDs – A brief history)
(Hard)多年来，硬盘驱动器主要用作存储设备。人们仍然在有硬盘的设备上工作。那么，是什么促使人们研究另一种大容量存储设备呢？SSD(SSDs)是如何诞生的？让我们回顾一下历史，了解SSD(SSDs)背后的动机。
在 1950 年代，有 2 种技术在使用类似于SSD(SSDs)的工作方式，即磁芯内存和卡电容只读存储。然而，由于更便宜的鼓存储单元的可用性，它们很快就被遗忘了。
IBM等公司在其早期的超级计算机中使用了SSD 。(SSDs)然而，SSD(SSDs)并不经常使用，因为它们价格昂贵。后来，在 1970 年代，General Instruments制造了一种名为 Electricly Alterable (Instruments)ROM的设备。这也没有持续多久。由于(Due)耐用性问题，该设备也没有获得普及。
1978 年，第一台SSD被石油公司用于采集地震数据。1979 年，StorageTek公司开发了第一款RAM SSD。
(RAM)基于RAM的SSD(SSDs)已经使用了很长时间。尽管它们更快，但它们消耗更多的CPU资源并且相当昂贵。1995 年初，开发了基于闪存的SSD(SSDs)。自推出基于闪存的SSD(SSDs)以来，某些需要出色MTBF（平均故障间隔时间）(MTBF (mean time between failures))率的行业应用程序将HDD(HDDs)替换为SSD(SSDs)。固态驱动器能够承受极端的冲击、振动和温度变化。因此，它们可以支持合理的 MTBF 率。(MTBF rates.)
固态硬盘如何工作？(How do Solid State Drives work?)
SSD(SSDs)是通过将互连的内存芯片堆叠在一个网格中来构建的。芯片由硅制成。改变堆栈中的芯片数量以实现不同的密度。然后，它们配有浮栅晶体管来保持电荷。因此，即使断开电源， SSD(SSDs)也会保留存储的数据。
任何 SSD 都可以具有三种内存类型(three memory types)之一——单级、多级或三级单元。
1.单层电池(Single level cells)是所有电池中最快、最耐用的。因此，它们也是最昂贵的。这些是为了在任何给定时间保存一位数据而构建的。
2.多级单元(Multi-level cells)可以保存两位数据。对于给定空间，它们可以容纳比单级单元更多的数据。但是，它们有一个缺点——它们的写入速度很慢。
3.三级电池(Triple-level cells)是最便宜的。它们不太耐用。这些单元可以在一个单元中保存 3 位数据。他们的写入速度是最慢的。
为什么要使用 SSD？(Why is an SSD used?)
(Hard Disk Drives)长期以来，硬盘驱动器一直是系统的默认存储设备。因此，如果公司正在转向SSD(SSDs)，或许有充分的理由。现在让我们看看为什么一些公司更喜欢将SSD(SSDs)用于他们的产品。
在传统的HDD中，您有电机来旋转盘片，并且 R/W 磁头会移动。在SSD中，存储由闪存芯片负责。因此，没有移动部件。这增强了设备的耐用性。(enhances the durability of the device.)
在带有硬盘的笔记本电脑中，存储设备将消耗更多的电力来旋转盘片。由于SSD(SSDs)没有移动部件，配备SSD(SSDs)的笔记本电脑消耗的能量相对较少。虽然公司正在努力构建在旋转时消耗更少功率的混合HDD ，但(HDDs)这些混合设备可能会比固态驱动器消耗更多的功率。(these hybrid devices will probably consume more power than a solid-state drive.)
好吧，看起来没有任何活动部件会带来很多好处。同样(Again)，没有旋转盘片或移动 R/W 磁头意味着几乎可以立即从驱动器中读取数据。使用SSD(SSDs)时，延迟会大大降低。因此(Thus)，带有SSD(SSDs)的系统可以运行得更快。
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硬盘(HDDs)需要小心处理。由于它们具有活动部件，因此它们既敏感又脆弱。有时，即使是轻微的跌落振动也会损坏HDD。但SSD(SSDs)在这里占据上风。它们比HDD(HDDs)更能承受冲击。但是，由于它们具有有限数量的写入周期，因此它们具有固定的寿命。一旦写入周期用完，它们就会变得不可用。
SSD 的类型(Types of SSDs)
SSD(SSDs)的某些功能受其类型的影响。在本节中，我们将讨论各种类型的SSD(SSDs)。
1. 2.5” -与列表中的所有SSD(SSDs)相比，这是最慢的。但它仍然比HDD快。这种类型以每 GB 的最优惠价格提供。它是当今使用的最常见的SSD类型。
2. mSATA - m 代表迷你。mSATA SSD(SSDs)比 2.5” SSD 快。它们在空间不是奢侈品的设备（如笔记本电脑和笔记本电脑）中是首选。它们的外形尺寸很小。虽然 2.5 英寸的电路板是封闭的，但 mSATA SSD(SSDs)中的电路板是裸露的。它们的连接类型也不同。
3. SATA III – 它具有与 SSD 和 HDD 兼容的连接。(This has a connection that is both SSD and HDD compliant.)当人们第一次开始从HDD过渡到(HDD)SSD时，这变得很流行。它是 550 MBps(MBps)的慢速。驱动器使用称为SATA(SATA)电缆的线连接到主板，因此它可能有点杂乱。
4. PCIe – PCIe代表Peripheral Component Interconnect Express。这是通常用于容纳图形卡、声卡等的插槽的名称。PCIe SSD(PCIe SSDs)使用此插槽。它们是最快的，自然也是最昂贵的。它们的速度几乎是SATA 驱动器(SATA drive)的四倍。
5. M.2 –像 m SATA驱动器一样，它们有一块裸露的电路板。M.2 驱动器在物理上是所有SSD(SSD)类型中最小的。这些平滑地靠在主板上。它们有一个很小的连接器引脚，占用的空间很小。由于(Due)它们的体积小，它们很快就会变热，尤其是在速度很高的时候。因此，它们配备了内置散热器/散热器。M.2 SSD(M.2 SSDs)有SATA和PCIe 两种类型(PCIe types)。因此，M.2 驱动器可以具有不同的大小和速度。虽然 mSATA 和 2.5 英寸驱动器不支持NVMe（我们将在接下来看到），但 M.2 驱动器可以。
6. NVMe – NVMe 代表Non-Volatile Memory express。该短语是指通过与PCI Express和 M.2等SSD(SSDs)的接口与主机交换数据。使用NVMe接口，可以实现高速。
SSD可以用于所有PC吗？(Can SSDs be used for all PCs?)
如果 SSD 能提供这么多，为什么没有完全取代 HDD 作为主要存储设备呢？( why have they not fully replaced HDDs as the main storage device?)对此的一个重要威慑是成本。虽然现在SSD的价格比以前低了，但当它进入市场时，HDD 仍然是更便宜的选择( HDDs are still the cheaper option)。与硬盘驱动器的价格相比，SSD的成本可能要高出近三倍或四倍。此外，随着您增加驱动器的容量，价格会迅速上涨。因此，它尚未成为所有系统在财务上可行的选择。
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SSD(SSDs)没有完全取代HDD(HDDs)的另一个原因是容量。带有 SSD 的典型系统可以具有 512GB 到 1TB 范围内的功率。但是，我们已经拥有具有数 TB 存储空间的HDD系统。(HDD)因此(Therefore)，对于追求大容量的人来说，HDD(HDDs)仍然是他们的首选。
限制(Limitations)
我们已经看到了SSD(SSD)发展背后的历史，SSD是如何构建的，它提供的好处，以及为什么它还没有在所有PCs/laptops上使用。然而，每一项技术创新都有其一系列缺点。固态硬盘的缺点是什么？
1.写入速度 –(Write speed –)由于没有移动部件，SSD可以立即访问数据。但是，只有延迟很低。当必须将数据写入磁盘时，需要先擦除以前的数据。因此， SSD(SSD)上的写入操作很慢。一般用户可能看不到速度差异。但是，当您要传输大量数据时，这是一个很大的劣势。
2.数据丢失和恢复——(Data loss and recovery –)在固态驱动器上删除的数据将永久丢失。(Data)由于没有数据的备份副本，这是一个巨大的缺点。敏感数据的永久丢失可能是一件危险的事情。因此，无法恢复从SSD丢失的数据这一事实是这里的另一个限制。
3.成本——(Cost –)这可能是暂时的限制。由于SSD(SSDs)是一种相对较新的技术，因此它们比传统HDD(HDDs)昂贵是很自然的。我们已经看到价格一直在下降。也许几年后，成本不会成为人们转向SSD(SSDs)的阻碍。
4.寿命——(Lifespan –)我们现在知道数据是通过擦除以前的数据写入磁盘的。每个 SSD(Every SSD)都有一定数量的写入/擦除周期。因此，当您接近写入/擦除周期限制时，SSD的性能可能会受到影响。平均SSD带有大约 1,00,000 次写入/擦除周期。这个有限的数字会缩短SSD的使用寿命。
5.存储——(Storage –)与成本一样，这也可能是暂时的限制。截至目前，SSD(SSDs)仅以小容量提供。对于更高容量的SSD(SSDs)，必须花很多钱。只有时间才能证明我们是否可以拥有容量大且价格合理的SSD 。(SSDs)
What is a Solid-State Drive (SSD)? SSD Definition
While buying a new laptop, you might have seen people debating whether a device with an HDD is better or one with an SSD. What is HDD here? We all are aware of the hard disk drive. It is a mass storage device used generally in PCs, laptops. It stores the operating system and other application programs. An SSD or Solid-State drive is a newer alternative for the traditional Hard Disk Drive. It has come into the market much recently instead of the hard drive, which has been the primary mass storage device for several years.
Although their function is similar to that of a hard drive, they are not built like HDDs or work like them. These differences make SSDs unique and give the device some benefits over a hard disk. Let us know more about Solid-State Drives, their architecture, functioning, and much more.
What is a Solid-State Drive (SSD)?
We know that memory can be of two types – volatile and non-volatile. An SSD is a non-volatile storage device. This means that data stored on an SSD stays even after the power supply is stopped. Due to their architecture (they are made up of a flash controller and NAND flash memory chips), solid-state drives are also called flash drives or solid-state disks.
SSDs – A brief history
Hard disk drives were predominantly used as storage devices for many years. People still work on devices with a hard disk. So, what pushed people to research an alternative mass storage device? How did SSDs come into being? Let us take a small peek into the history to know the motivation behind SSDs.
In the 1950s, there were 2 technologies in use similar to the way SSDs work, namely, magnetic core memory and card-capacitor read-only store. However, they soon faded into oblivion due to the availability of cheaper drum storage units.
Companies such as IBM used SSDs in their early supercomputers. However, SSDs were not used often because they were expensive. Later, in the 1970s, a device called Electrically Alterable ROM was made by General Instruments. This, too, did not last long. Due to durability issues, this device also did not gain popularity.
In the year 1978, the first SSD was used in oil companies to acquire seismic data. In 1979, the company StorageTek developed the first-ever RAM SSD.
RAM-based SSDs were in use for a long time. Although they were faster, they consumed more CPU resources and were quite expensive. In early 1995, flash-based SSDs were developed. Since the introduction of flash-based SSDs, certain industry applications that require an exceptional MTBF (mean time between failures) rate, replaced HDDs with SSDs. Solid-state drives are capable of withstanding extreme shock, vibration, temperature change. Thus they can support reasonable MTBF rates.
How do Solid State Drives work?
SSDs are built by stacking together interconnected memory chips in a grid. The chips are made of silicon. The number of chips in the stack is changed to achieve different densities. Then, they are fitted with floating gate transistors to hold a charge. Therefore, stored data is retained in SSDs even when they are disconnected from the power source.
Any SSD can have one of the three memory types – single-level, multi-level or triple-level cells.
1. Single level cells are the fastest and most durable of all cells. Thus, they are the most expensive too. These are built to hold one bit of data at any given time.
2. Multi-level cells can hold two bits of data. For a givens space, they can hold more data than single-level cells. However, they have a disadvantage – their write speed is slow.
3. Triple-level cells are the cheapest of the lot. They are less durable. These cells can hold 3 bits of data in one cell. They write speed is the slowest.
Why is an SSD used?
Hard Disk Drives have been the default storage device for systems, for quite a long time. Thus, if companies are shifting to SSDs, there is perhaps a good reason. Let us now see why some companies prefer SSDs for their products.
In a traditional HDD, you have motors to spin the platter, and the R/W head moves. In an SSD, storage is taken care of by flash memory chips. Thus, there are no moving parts. This enhances the durability of the device.
In laptops with hard drives, the storage device will consume more power to spin the platter. Since SSDs are devoid of moving parts, laptops with SSDs consume relatively lesser energy. While companies are working to build hybrid HDDs which consume lesser power while spinning, these hybrid devices will probably consume more power than a solid-state drive.
Well, it looks like not having any moving parts comes with plenty of benefits. Again, not having spinning platters or moving R/W heads implies that data can be read from the drive almost instantly. With SSDs, the latency decreases considerably. Thus, systems with SSDs can operate faster.
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HDDs need to be handled carefully. As they have moving parts, they are sensitive and fragile. Sometimes, even a small vibration from a drop can damage the HDD. But SSDs have the upper hand here. They can withstand impact better than HDDs. However, since they have a finite number of write cycles, they have a fixed lifespan. They become unusable once the write cycles are exhausted.
Types of SSDs
Some of the features of SSDs are influenced by their type. In this section, we shall discuss the various types of SSDs.
1. 2.5” – Compared to all the SSDs on the list, this is the slowest. But it is still faster than HDD. This type is available at the best price per GB. It is the most common type of SSD in use today.
2. mSATA – m stands for mini. mSATA SSDs are faster than 2.5” ones. They are preferred in devices (such as laptops and notebooks) where space is not a luxury. They have a small form factor. While the circuit board in 2.5” is enclosed, the ones in mSATA SSDs are bare. Their connection type also differs.
3. SATA III – This has a connection that is both SSD and HDD compliant. This became popular when people first started transitioning to SSD from HDD. It is slow speed of 550 MBps. The drive is connected to the motherboard using a cord called the SATA cable so that it can be a bit cluttered.
4. PCIe –PCIe stands for Peripheral Component Interconnect Express. This is the name given to the slot that usually houses graphic cards, sounds cards, and the like. PCIe SSDs use this slot. They are the fastest of all and naturally, the most expensive too. They can reach speeds that are almost four times higher than that of a SATA drive.
5. M.2 – Like mSATA drives, they have a bare circuit board. M.2 drives are physically the smallest of all SSD types. These lie smoothly against the motherboard. They have a tiny connector pin and take up very little space. Due to their small size, they can quickly become hot, especially when the speed is high. Thus, they come with a built-in heatsink/heat spreader. M.2 SSDs are available in both SATA and PCIe types. Therefore, M.2 drives can be of varying sizes and speeds. While mSATA and 2.5” drives cannot support NVMe (which we will see next), M.2 drives can.
6. NVMe – NVMe stands for Non-Volatile Memory express. The phrase refers to the interface through with SSDs such as PCI Express and M.2 exchange data with the host. With an NVMe interface, one can achieve high speeds.
Can SSDs be used for all PCs?
If SSDs have so much to offer, why have they not fully replaced HDDs as the main storage device? A significant deterrent to this is the cost. Although the price of SSD is now lesser than what it was, when it made an entry into the market, HDDs are still the cheaper option. Compared to the price of a hard drive, an SSD can cost almost thrice or four times higher. Also, as you increase the capacity of the drive, the price quickly shoots up. Therefore, it has not yet become a financially viable option for all systems.
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Another reason why SSDs have not fully replaced HDDs is capacity. A typical system with an SSD can have power in the range of 512GB to 1TB. However, we already have HDD systems with several terabytes of storage. Therefore, for people who are looking at large capacities, HDDs are still their go-to option.
Limitations
We have seen the history behind the development of SSD, how an SSD is built, the benefits it provides, and why it has not been used on all PCs/laptops yet. However, every innovation in technology comes with its set of drawbacks. What are the disadvantages of a solid-state drive?
1. Write speed – Due to the absence of moving parts, an SSD can access data instantly. However, only latency is low. When data has to be written on the disk, previous data needs to be erased first. Thus, write operations are slow on an SSD. The speed difference may not be visible to the average user. But it is quite a disadvantage when you want to transfer huge amounts of data.
2. Data loss and recovery –Data deleted on solid-state drives is lost permanently. Since there is no backed-up copy of data, this is a huge disadvantage. Permanent loss of sensitive data can be a dangerous thing. Thus, the fact that one cannot recover data lost from an SSD is another limitation here.
3. Cost – This could be a temporary limitation. Since SSDs are a relatively newer technology, it is only natural that they are expensive than traditional HDDs. We have seen that the prices have been reducing. Maybe in a couple of years, the cost will not be a deterrent for people to shift to SSDs.
4. Lifespan – We now know that data is written to the disk by erasing previous data. Every SSD has a set number of write/erase cycles. Thus, as you near the write/erase cycle limit, the SSD’s performance may be affected. An average SSD comes with about 1,00,000 write/erase cycles. This finite number shortens the lifespan of an SSD.
5. Storage – Like cost, this can again be a temporary limitation. As of now, SSDs are available only in a small capacity. For SSDs of higher capacities, one must shell out a lot of money. Only time will tell whether we can have affordable SSDs with good capacity.
