固态硬盘 ( SSD(SSDs) ) 正迅速成为操作系统和应用程序的首选计算机存储。您会在最新的笔记本电脑、手机、平板电脑甚至游戏机中找到它们。
凭借出色的性能和耐用性，这些驱动器正在引起轰动，但SSD(SSD)到底是什么？
传统硬盘驱动器(Hard Disk Drives)( HDD(HDDs) ) 的工作原理
要了解SSD(SSDs)的不同之处，我们需要简要回顾一下传统的硬盘驱动器(Hard Disk Drives)( HDD(HDDs) )。直到最近，HDD是几乎所有计算机中都可以找到的标准驱动器类型。
在HDD内，您会发现一个或多个称为“盘片”的旋转磁盘。每个盘片分为磁道和扇区。盘片通常由铝或玻璃制成，并涂有磁性材料。
盘片的表面包含数十亿个单独的区域，每个区域代表一个数据位。该区域可以被磁化或去磁，代表一或零。
当旋转的盘片以每分钟数千转的速度移动时，连接在摆动臂上的微型读写头在盘片上方漂浮着头发的宽度，从驱动器读取或写入驱动器。
硬盘(Hard)驱动器是极其复杂的设备，具有许多微小、精确且易碎的移动部件。他们工作得和他们一样好，这是一个现代奇迹。
固态硬盘 (SSD) 的工作原理
与硬盘驱动器相比，SSD 与CPU(CPUs)和RAM等半导体设备的共同点更多。SSD(SSDs)和HDD(HDDs)都充当存储设备，但SSD(SSDs)的工作方式非常不同。
在典型的SSD中，您只会找到计算机芯片。SSD的控制器芯片负责管理数据的存储方式和存储位置，但SSD的大部分由闪存芯片组成。
闪存(Flash)是“非易失性”存储器。像RAM一样的(RAM)易失性(Volatile)内存在断电时不会持续存在——存储在那里的数据会消失。相比之下，使用非易失性内存（如SSD(SSDs)或USB驱动器），即使关闭电源，您的数据也会保留。这就是为什么USB拇指驱动器也被称为“闪存驱动器”的原因！
现代SSD(SSDs)（以及大多数USB闪存驱动器和存储卡）使用一种称为NAND闪存的闪存。它以您可以在微芯片中制作的一种逻辑门类型命名。在NAND存储器中，有一些“单元”可以保持不同的电荷水平。通过测量存储单元中的电荷水平，您可以判断它是代表 1 还是代表 0。要更改单元格的内容，您只需更改其中的电荷水平。
NAND存储器领域的技术有许多不同的变化。例如，您可能已经看到一些标有“ V-NAND ”或“垂直”NAND的(” NAND)三星 SSD(Samsung SSDs)。在这里，存储单元垂直堆叠，允许在相同的硅足迹中提供更多的存储容量。英特尔的 3D NAND也或多或少是相同的技术。
SSD 类型和接口
SSD(SSDs)有多种外形尺寸和NAND闪存类型。这决定了SSD的最大性能及其价格。
闪存类型
所有NAND闪存的数据密度和性能都不相同。您会从我们上面的讨论中回忆起，SSD(SSDs)将数据作为电荷存储在内存单元中。
如果一个单元只存储一位数据，则称为SLC或单级单元存储器(single-level cell memory)。MLC（多级单元）和TLC（三级单元）存储器分别存储每个单元的两位和三位数据。QLC（四级单元）存储器将其提高到每个单元四位。
您可以在单个单元中存储的数据位越多，SSD 的价格就越便宜，或者您可以将更多的数据塞入同一空间。这听起来是个好主意，但由于SSD(SSDs)的运行方式，使用多位存储方法时驱动器会更快地死掉。SLC内存是性能最好、最耐用的NAND类型，使用寿命长。然而，它也是迄今为止最昂贵的，并且只在高端驱动器中找到。
因此，大多数消费级 SSD(SSDs)使用MLC或TLC，并采用特殊方法尽可能延长其使用寿命。我们将在本文稍后的技术缺点下讨论SSD磨损的问题。(SSD)
SSD 外形尺寸
SSD(SSDs)有多种形式。“外形尺寸”只是设备的物理形状及其符合的连接标准。由于SSD(SSDs)最初设计用于替代HDD(HDDs)，因此用于消费类台式机的第一批设备旨在插入以前的硬盘驱动器。
这就是2.5 英寸 SATA SSD( 2.5-inch SATA SSD)设计的用武之地。您只需取出当前的 2.5 英寸笔记本电脑硬盘驱动器，然后插入其中一个SSD(SSDs)。
这个外壳内的SSD不需要那么多空间，但它非常有意义，因为笔记本电脑和大多数现代台式机的主板上已经有 2.5 英寸驱动器托架和SATA连接器。(SATA)您还可以购买适配器，以便将 2.5 英寸驱动器放入台式机的 3.5 英寸托架中。
除了占用不必要的空间外，这些 2.5 英寸驱动器还被限制为 600 MB/s，因为这是SATA 3接口的限制。
mSATA (mini-SATA) 标准解决了空间问题。mSATA 在物理上与PCI Express Mini(PCI Express Mini)卡标准具有相同的形状、大小和连接器，但是这两种类型的卡在电气上不兼容。
m SATA标准现已被 M.2 标准取代。M.2 SSD(M.2 SSDs)可以是SATA或PCIe，具体取决于卡和主板组合。
M.2 卡也可以是双面的，两面都有组件，它们的长度各不相同。确保您的计算机主板与您要使用的M.2 SSD兼容始终很重要！(M.2 SSD)
NVMe SSD(NVMe SSDs)使用 Non-Volatile Memory Express标准，这就是计算机可以使用更常用于显卡的PCIe访问(PCIe)SSD内存的方式。PCIe比(PCIe)SATA拥有更多的带宽，让快速SSD内存充分发挥其潜力。
SSD的优势
SSD(SSDs)迅速成为存储技术标准的原因有很多。虽然一些早期的问题使它们暂时脱离了主流计算机世界，但它们现在已经到了我们可以向任何人推荐它们的地步。即使是最新的视频游戏机(latest video game consoles)现在也使用SSD。以下是导致SSD(SSDs)目前受欢迎的关键优势。
SSD 速度很快
全球最快的机械硬盘，希捷 Mach.2 (Seagate Mach.2) Exos 2X14，可以达到 524 MB/s持续传输速率。这几乎与SATA 3 SSD一样快，但是如果您正在寻找市场的高端产品，那么如今您在计算机中发现的典型机械驱动器可以达到 100 MB/s和 250 MB/s之间的速度.
典型的M.2 PCIe SSD(M.2 PCIe SSDs)，例如中端笔记本电脑中的那些，提供 2.5 到 3.5 GB/s。最新的M.2 PCIe SSD(M.2 PCIe SSDs)接近 8 GB/s，这是一个令人难以置信的数据量。顺序(Sequential)写入速度通常比读取速度慢一点，但数据在两个方向上都以惊人的速度飞行。
这也不仅仅是传输速度。机械硬盘驱动器需要时间旋转盘片并将驱动器磁头移动到位。在盘片上为数据请求找到正确的位置称为“寻道时间”。对于SSD(SSDs)，该延迟数实际上为零。
SSD可以立即从其存储单元中的任何位置读取数据，甚至可以并行执行。无论您采用哪种方式切片，SSD(SSDs)都处于与最好的机械硬盘驱动器不同的性能领域，无论您采用哪种方式切片。
将计算机的HDD升级到SSD时，您会体验到更快的启动时间和非常快速的系统响应能力。仅仅(Simply)是因为您的CPU无需等待来自存储驱动器的数据。这是让旧的Windows(Windows)系统焕然一新的绝妙方式。
SSD 经久耐用
SSD(SSDs)的耐用性与任何其他固态组件（例如没有移动部件的CPU或RAM ）一样耐用。(RAM)除非电涌将它们摧毁，否则它们应该无限期地运行，或者至少只要计算机对您仍然有用。闪存(Flash)也非常耐冲击损坏，这与硬盘驱动器不同，如果它们掉落很容易损坏，尤其是在盘片旋转时。
这种耐用性使其非常适合笔记本电脑，这也是Apple MacBook Air、i Mac和(Mac)Mac计算机系列的其他成员等超级本拥有高性能集成SSD(SSDs)的原因。
在这种情况下， “耐用(Durability)性”并不是指SSD磨损现象，我们将在下面的缺点列表中进行介绍。
SSD 不会受到碎片的影响(Suffer From Fragmentation)
数据碎片是(Data)HDD(HDDs)上的一个真正问题。当新数据写入驱动器上的第一个可用空间时，就会发生这种情况。因此，给定文件或一组相关文件的数据可能分散在驱动器的物理盘片区域。
这会破坏顺序读取速度并增加大量寻道时间，因为驱动器磁头到处飞来寻找文件的所有部分。SSD(SSDs)，由于它们的本质，不会受到碎片的影响。并不是文件没有碎片化。只是没关系，因为没有活动部件，也没有时间可言。
碎片整理只会给驱动器带来不必要的磨损。如果您想了解更多关于SSD碎片的信息，请阅读您应该对 SSD 进行碎片整理吗？(Should You Defrag an SSD?)
SSD 很安静
硬盘噪音大！电机的嗡嗡声、磁盘的嗖嗖声、驱动磁头来回移动的咔嗒声——这些都是几十年来计算机用户的背景噪音。
(SSDs)相比之下，SSD完全没有噪音。这似乎是一个微不足道的优势，但嘈杂的计算机组件很烦人。在某些用例中，例如用于录音的计算机，声级至关重要。已经有昂贵的硬盘驱动器具有特殊的安装和设计，试图抑制硬盘(HDD)驱动器的噪音，但使用固态硬盘(SSDs)，问题就完全解决了。
这就是为什么我们现在可以拥有像Apple M1 MacBook Air这样没有风扇和机械硬盘的电脑。整个计算机都是固态的，因此不会发出任何噪音！
SSD 体积小，能效高
SSD 占用的空间比HDD(HDDs)少得多，而且它们工作所需的电力也少得多。这意味着我们可以拥有更小更薄的计算机、平板电脑、智能手机和其他需要快速非易失性存储驱动器的电子设备。
SSD在不使用时几乎可以完全进入睡眠状态，并且与HDD(HDDs)不同，它们几乎可以立即切换到高性能模式。总体(Taken)而言，SSD功耗对于从移动计算机和其他使用它们的小工具获得更长的电池寿命尤为重要。机电设备只需要比固态设备更多的能量来运行。
SSD 可以缩小安装尺寸
SSD(SSDs)可以减少某些应用程序的安装大小，尤其是视频游戏(video games)。当应用程序依赖于快速将数据流式传输到内存中时，开发人员可能会在HDD盘片上的多个位置复制信息。这减少了寻道时间，因为驱动器磁头始终接近所需数据的副本。这是一个聪明的技巧，但它是以牺牲存储空间为代价的。
为SSD(SSDs)设计的应用程序根本不需要这样做。由于SSD几乎没有延迟，并且可以立即从驱动器上的任何位置读取数据，因此只需存在一份数据副本。
PlayStation 5等游戏机已经展示了SSD(SSDs)可以缩小多少安装尺寸，尤其是结合压缩，这为我们带来了下一个优势。
SSD 可以加速
如果您认为SSD(SSDs)已经足够快，您可以加速这些驱动器以获得一些真正的高速性能数据。这一切都归功于压缩技术。数据以高度压缩的形式存储在SSD上。(SSD)当请求信息时，它会实时解压缩，有效放大SSD的原始数据传输速度。
唯一的问题是你需要一个强大的处理器来解压缩，但SSD(SSDs)目前不包括这样的处理器。事实证明，GPU(GPUs)非常擅长做这类工作，因此使用软件API(APIs)（应用程序接口(Application Programmer Interface)），如微软的DirectStorage和Nvidia 的 RTX IO(Nvidia’s RTX IO)，最近几代GPU不仅可以加速 3D 图形，还可以加速SSD性能。
SSD的缺点
SSD(SSDs)有许多理想的属性，但技术并不完美。SSD所有权的某些方面并不像我们希望的那样令人愉快。
SSD 更贵
HDD的价格已经大幅下降，并且它们可以存储的数据量已经增加到了疯狂的密度水平。结果是一千兆字节的HDD数据成本甚至比最便宜的 NAND 闪存还要低。
SSD价格在过去几年中急剧下降，但人们通常仍在使用 256GB 至 512GB 范围内的相对较小的SSD(SSDs)。SSD(SSDs)是为应用程序和操作系统保留的，而HDD(HDDs)仍然为无法从SSD速度中受益的媒体文件或应用程序提供大容量存储。
好消息是，与所有半导体技术一样，晶体管密度和制造工艺可能会呈现指数趋势，从而降低成本并占用更多空间。目前，大多数预算都要求混合使用SSD和HDD存储。
SSD 可能会磨损
虽然SSD(SSDs)非常耐用，并且可以承受比HDD(HDDs)更多的惩罚，同时还具有更长的使用寿命，但它们会受到磨损。SSD磨损的发生是因为SSD(SSDs)写入内存单元具有破坏性。每次向SSD存储单元写入一个位时，它就会失去一点点保持电荷的能力。
随着时间的推移，对单元的重复写入使其无法操作。SLC SSD(SLC SSDs)可以在炸掉给定单元之前处理最多的重复写入，但MLC、TLC和QLC单元按此顺序更容易受到攻击。早期的消费级 SSD(SSDs)可能很快就会以惊人的速度消失，但今天的驱动器采用了磨损均衡和过度配置等策略来延长SSD的写入寿命。
SSD磨损是一个复杂的话题，因此请查看您需要了解的关于 SSD 磨损的所有信息(Everything You Need To Know About SSD Wear & Tear)以进行深入讨论。
SSD 可能会出现快速位腐烂
所有形式的数据存储最终都会屈服于位腐烂。(bit rot.)当存储介质退化到无法再以可读形式保存数据时，就会发生这种情况。
由于各种原因，不同的介质会出现位损坏，但硬盘驱动器可以存储数十年而不会出现位损坏问题。另一方面，SSD可能会在存储几年后丢失数据。(SSDs)这是由于保持每个存储单元中的电荷的绝缘层退化所致。如果金额泄漏，则单元格为空且不包含任何数据！
如果将SSD(SSDs)保存在过热的环境中，似乎位腐烂发生得更快，但无论哪种方式，它们都可能不是将数据存储在某个地方的抽屉中的最佳选择。
SSD 数据恢复(SSD Data Recovery Is Hard)几乎不可能
围绕从机械硬盘恢复数据的艺术建立了一个复杂的行业。如果您有足够的钱可以花钱，您甚至可以从损坏的驱动器中恢复数据，因为专家会从字面上重建驱动器。
在更普通的层面上，您可以恢复意外删除的数据，因为当您在Windows或其他操作系统中删除物理数据时， HDD(HDDs)不会删除它们。相反，驱动器的该区域被简单地标记为被覆盖。只要覆盖尚未发生，您就可以使用特殊软件将其恢复。
如果驱动器损坏或文件被删除， SSD(SSDs)几乎不可能恢复任何东西。如果HDD 被(HDD is damaged)电涌损坏，您仍然可以使用新的驱动电子设备对其进行重建，但由于SSD完全是电气的，因此所有内存都可能被烧毁。
SSD(SSDs)具有复杂的控制器，这些控制器对他们不知道的物理数据操作系统做很多事情，这也无济于事。例如，SATA SSD使用的(SATA SSDs)TRIM命令会抢先删除已标记为删除的内存单元，以加快写入新数据的过程。所以取消删除的技巧对他们不起作用！
未来是固态的
尽管SSD(SSDs)并不完美，但它们代表了存储驱动器性能的飞跃，以至于它们最终在存储市场上占据主导地位似乎是不可避免的。随着时间的推移，我们预计即使是SLC SSD(SLC SSDs)的价格也会下降，而不太耐用的SSD类型在限制磨损方面会变得更加智能。
硬盘(Hard)技术在早期也存在相当多的问题，但我们感觉SSD(SSDs)仍然存在的任何问题都将在创纪录的时间内得到解决。
What Is a Solid State Drive (SSD)? Plus, the Pros and Cons
Sоlid Ѕtate Drives (SSDs) are quickly becoming the preferred computer storage for operating systems and apps. You’ll find them in the latest laptops, phones, tablets, and even consoles.
With excellent performance and durability, these drives are making a real splash, but what exactly is an SSD?
How Traditional Hard Disk Drives (HDDs) Work
To grasp what makes SSDs different, we need to briefly turn back the clock and look at traditional Hard Disk Drives (HDDs). An HDD was the standard type of drive you’d find in virtually all computers until recently.
Inside the HDD, you’ll find one or more spinning disks called “platters.” Each platter is divided into tracks and sectors. The platters are usually made from either aluminum or glass and are coated with magnetic material.
The platter’s surface contains billions of individual areas that each represent a single bit of data. The area can be magnetized or demagnetized, representing a one or a zero.
As the spinning platters move at thousands of revolutions per minute, tiny read-write heads attached to swinging arms float a hair’s breadth above the platter reading from or writing to the drive.
Hard disk drives are incredibly complicated devices with many tiny, precise, and fragile moving parts. It’s a modern marvel that they work as well as they do.
How a Solid State Drive (SSD) Works
SSDs have more in common with semiconductor devices like CPUs and RAM than hard disk drives. SSDs and HDDs both act as storage devices, but SSDs work in a very different way.
Inside a typical SSD, you’ll find only computer chips. There’s the SSD’s controller chip, which manages how and where data is stored, but the bulk of an SSD consists of flash memory chips.
Flash memory is “non-volatile” memory. Volatile memory, like RAM, does not persist when power is turned off—the data stored there disappears. By contrast, with non-volatile memory (like SSDs or USB drives), your data persists even when the power is turned off. This is why USB thumb drives are also referred to as “flash drives”!
Modern SSDs (and most USB flash drives and memory cards) use a type of flash memory called NAND flash memory. It’s named after one of the types of logic gates you can make in a microchip. Within NAND memory, there are “cells” that can hold different electrical charge levels. By measuring the charge level in a memory cell, you can tell whether it represents a one or a zero. To change the contents of a cell, you simply alter the level of charge inside it.
There are many different variations in the technology within the world of NAND memory. For example, you may have seen some Samsung SSDs labeled “V-NAND” or “vertical” NAND. Here the memory cells are stacked vertically, allowing for more storage capacity in the same silicon footprint. Intel’s 3D NAND is also more or less the same technology.
Types of SSDs and Interfaces
SSDs come in a variety of form factors and NAND flash memory types. This determines the maximum performance of an SSD as well as its price.
Flash Memory Types
All NAND flash isn’t the same for data density and performance. You’ll recall from our discussion above that SSDs store data as electrical charges inside memory cells.
If a cell only stores a single bit of data, it’s called SLC or single-level cell memory. MLC (multi-level cell) and TLC (triple-level cell) memory store two and three bits of data per cell, respectively. QLC (quad-level cell) memory takes it to four bits per cell.
The more bits of data you can store in a single cell, the cheaper your SSD can be, or the more data you can stuff into the same space. This sounds like a great idea, but thanks to how SSDs operate, drives die more quickly when using a multi-bit storage method. SLC memory is the best-performing and most durable type of NAND with a long lifespan. However, it’s also the most expensive by far and only found in high-end drives.
As such, most consumer SSDs use MLC or TLC and employ special methods to extend their useful lifespans as much as possible. We’ll cover the issue of SSD wear a little later in this article under the disadvantages of the technology.
SSD Form Factors
SSDs come in various form factors. A “form factor” is simply the physical shape of the device and what connection standard it conforms to. Because SSDs were initially designed to replace HDDs, the first devices meant for consumer desktops were intended to slot in where hard drives were before.
This is where the 2.5-inch SATA SSD design comes into the picture. You can simply take out your current 2.5-inch laptop hard drive and plug one of these SSDs in.
The SSD inside this casing doesn’t need all that room, but it made perfect sense since laptops and most modern desktops already have 2.5-inch drive bays and SATA connectors on their motherboards. You can also purchase adapters that let you place a 2.5-inch drive into a desktop’s 3.5-inch bay.
Apart from taking up unnecessary space, these 2.5-inch drives were limited to 600 MB/s since that’s the limit of the SATA 3 interface.
The mSATA (mini-SATA) standard solves the space issue. mSATA was physically the same shape, size, and connector as the PCI Express Mini card standard, but the two types of cards are electrically incompatible.
The mSATA standard has now been replaced by the M.2 standard. M.2 SSDs can be SATA or PCIe, depending on the card and the motherboard combination.
M.2 cards can also be double-sided with components on both sides, and they vary in length. It’s always important to make sure that your computer’s motherboard is compatible with the M.2 SSD you want to use with it!
NVMe SSDs use the Non-Volatile Memory Express standard, which is how the computer can access SSD memory using the PCIe that’s more commonly used for graphics cards. PCIe has much more bandwidth than SATA, allowing fast SSD memory to reach its full potential.
The Advantages of SSDs
There are many reasons why SSDs are rapidly becoming the standard in storage technology. While some early teething troubles kept them out of the mainstream computer world for a while, they are now at the point where we can recommend them to anyone. Even the latest video game consoles now use SSD. Here are the key strengths that have led SSDs towards their current popularity.
SSDs Are Fast
The fastest mechanical hard drive globally, the Seagate Mach.2 Exos 2X14, can reach sustained transfer rates of 524 MB/s. That’s very nearly as fast as a SATA 3 SSD, but the typical mechanical drive you’ll find in computers these days can achieve somewhere between 100 MB/s and 250 MB/s if you’re looking at the high-end of the market.
Typical M.2 PCIe SSDs, such as those found in mid-range laptops, offer 2.5 to 3.5 GB/s. The latest M.2 PCIe SSDs are getting close to 8 GB/s, which is a mind-boggling amount of data. Sequential write speeds are usually a little slower than read speeds, but data is flying at a tremendous pace in both directions.
It’s not just about transfer speeds, either. Mechanical hard drives need time spinning up platters and moving drive heads into place. Finding the right spot on the platter for a data request is known as “seek time”. For SSDs, that latency number is effectively zero.
SSD can instantly read data from any location within its memory cells and even do it in parallel. No matter which way you slice it, SSDs are in a different performance universe than even the best mechanical hard drives, no matter which way you slice it.
When upgrading a computer’s HDD to an SSD, you experience much faster boot times and very snappy system responsiveness. Simply because your CPU never has to wait for data from your storage drives. It’s a fantastic way to give an old Windows system new life.
SSDs Are Durable
SSDs are about as durable as any other solid-state component such as a CPU or RAM with no moving parts. Unless a power surge destroys them, they should run indefinitely or at least as long as the computer remains useful to you. Flash memory is also very resistant to impact damage, unlike hard drives that are easily destroyed if they fall, especially while the platters are spinning.
This durability makes them perfect for laptops, and it’s why ultrabooks such as the Apple MacBook Air, iMac, and other members of the Mac computer family have high-performance integrated SSDs.
“Durability” in this case doesn’t refer to the phenomenon of SSD wear, which we’re covering under the list of disadvantages below.
SSDs Don’t Suffer From Fragmentation
Data fragmentations are a real problem on HDDs. It happens when new data is written to the first available space on the drive. So a given file or set of related files might have their data scattered all over the physical platter area of the drive.
This destroys sequential read speeds and adds a ton of seek time because the drive heads are flying all over the place to find all the parts of a file. SSDs, due to their very nature, don’t suffer from fragmentation. It’s not that files aren’t fragmented. It’s just that it doesn’t matter because there are no moving parts and no seek time to speak of.
Defragmenting just puts unnecessary wear on the drive. If you want to know a little more about SSD fragmentation, read Should You Defrag an SSD?
SSDs are Quiet
Hard drives are noisy! The hum of the motor, the whoosh of the disk, the clicking sounds of the drive heads moving back and forth — that’s been the background noise for computer users over the decades.
SSDs, in contrast, make no noise at all. This might seem like a trivial advantage, but noisy computer components are annoying. In some use cases, such as computers used for sound recording, sound levels are critical. There have been expensive hard drives with special mountings and designs that have tried to curb HDD noise, but with SSDs, the problem is completely solved.
This is why we can now have a computer like the Apple M1 MacBook Air, which has no fans and no mechanical hard drive. The entire computer is solid-state and therefore makes no noise whatsoever!
SSD are Small and Power Efficient
SSDs take up way less room than HDDs, and they need much less power to work. That means we can have smaller and thinner computers, tablets, smartphones, and other electronic devices that require fast non-volatile storage drives.
SSDs can go almost entirely to sleep when not in use, and, unlike HDDs, they can switch to high-performance mode almost instantly. Taken as a whole, SSD power consumption is especially important to get better battery life from mobile computers and other gadgets that use them. Electromechanical devices simply need more energy than solid-state devices to operate.
SSDs Can Shrink Installation Sizes
SSDs can reduce the installation sizes of some applications, especially video games. When applications rely on data streaming into memory rapidly, the developers may duplicate information in multiple locations on the HDD platter. This cuts down on seek times because the drive heads are always close to a copy of the data it needs. It’s a clever trick, but it comes at the expense of storage space.
Applications designed for SSDs don’t need to do this at all. Since the SSD has virtually no latency and can read data from anywhere on the drive immediately, only one copy of the data must be present.
Consoles like the PlayStation 5 have already shown how much SSDs can shrink install sizes, especially combined with compression, which brings us to the next advantage.
SSDs Can Be Accelerated
If you thought that SSDs were already plenty fast, you could speed up these drives for some truly high-speed performance numbers. It’s all thanks to compression technology. The data is stored on the SSD in a heavily-compressed form. When the information is requested, it’s decompressed in real-time, effectively amplifying the raw data transfer speeds of the SSD.
The only catch is that you need a powerful processor to decompress, but SSDs currently don’t include such a processor. It turns out that GPUs are excellent at doing this type of work, so using software APIs (Application Programmer Interface) such as Microsoft’s DirectStorage and Nvidia’s RTX IO, recent generations of GPU can accelerate not just 3D graphics but SSD performance as well.
The Disadvantages of SSDs
SSDs have many desirable attributes, but the technology isn’t perfect. Some aspects of SSD ownership aren’t quite as pleasant as we’d like.
SSDs are More Expensive
HDDs have come down in price so much and have increased the amount of data they can store to insane levels of density. The result is that a gigabyte of HDD data costs much less than even the cheapest NAND flash.
SSD prices have fallen precipitously over the last few years, but folks are generally still using relatively small SSDs in the 256GB to 512GB range. SSDs are reserved for applications and operating systems, while HDDs still have mass storage for media files or applications that don’t benefit from SSD speeds.
The good news is that, like all semiconductor technology, transistor density and manufacturing processes are likely to show an exponential trend leading to lower cost and more significant amounts of space. For now, most budgets call for a mix of SSD and HDD storage.
SSDs Can Wear Out
While SSDs are very durable and can stand up to more punishment than HDDs, while also having longer operational lives, they suffer from wear. SSD wear happens because SSDs write to memory cells is destructive. Every time a bit is written to an SSD memory cell, it loses its ability to hold a charge just a little.
Over time, repeated writes to a cell make it inoperable. SLC SSDs can handle the most repeated writes before frying a given cell, but MLC, TLC, and QLC cells are more vulnerable, in that order. Early consumer SSDs could die alarmingly soon, but today drives have strategies such as wear leveling and overprovisioning to extend the write endurance of the SSD.
SSD wear is a complex topic, so have a look at Everything You Need To Know About SSD Wear & Tear for an in-depth discussion.
SSDs Can Have Rapid Bit Rot
All forms of data storage eventually succumb to bit rot. This happens when the storage medium degrades so much that it can no longer hold the data in a readable form.
Different media get bit rot for various reasons, but hard drives can be stored for decades without bit rot being a problem. SSDs, on the other hand, can potentially lose their data after only a few years of storage. This happens due to the degradation of the insulating layer that keeps the charge in each memory cell. If the amount leaks out, the cell is empty and contains no data!
It seems that bit rot happens more quickly if SSDs are kept in an environment that’s too hot, but either way, they probably aren’t the best choice for storing data in a drawer somewhere.
SSD Data Recovery Is Hard to Impossible
There’s a sophisticated industry built around the art of recovering data from mechanical hard drives. If you have enough money to spend, you can even recover data from drives that have been smashed up, as a specialist literally rebuilds the drive from pieces.
On a more mundane level, you can recover data that’s been accidentally deleted because HDDs don’t delete the physical data when you delete them in Windows or another operating system. Instead, that area of the drive is simply marked to be overwritten. As long as the overwriting hasn’t happened yet, you can recover it using special software.
SSDs make it almost impossible to recover anything if the drive is damaged or files are deleted. If an HDD is damaged by an electrical surge, you can still rebuild it with new drive electronics, but since an SSD is entirely electrical, all of the memory could be fried.
It also doesn’t help that SSDs have sophisticated controllers that do a lot of things with physical data operating systems they don’t know about. For example, the TRIM command used by SATA SSDs pre-emptively deletes memory cells that have been marked for deletion to speed up the process of writing new data. So the undelete trick won’t work on them!
The Future Is Solid-State
While SSDs aren’t perfect, they represent such a leap in storage drive performance that their eventual dominance of the storage market seems inevitable. Over time we expect even SLC SSDs to come down in price, while less durable SSD types will become even smarter when it comes to limiting wear.
Hard drive technology also had its fair share of problems in the early days, but we have a feeling whatever issues SSDs still have will be solved in record time.
