SSDs - Part 1 - Why do I need one?

  • Thursday, Jan 30, 2020

One of the most frequent requests for support I receive is that a client’s computer is running slowly. Without hesitation, my first port of call is to recommend an upgrade to a Solid State Drive (SSD) - assuming the machine doesn’t already have one and that the machine is upgradeable (more on this in Part 3 ). Unless you bought your computer very recently, it’s likely that it would have come with a Hard Disk Drive (HDD). So why do I recommend upgrading to an SSD? First, we need to go through a brief history of computer storage.




Hard Disk Drives - The Old Reliable


Inside a hard drive

For years, computers have had hard disk drives inside them. These are based on a mechanical design where the information is stored on platters made of metal, glass or ceramic substrate. When the hard drive wants to access the data, a spindle spins these platters, and a read/write head reads the data through the logic board and out of the connections to your computer. If you listen closely to a computer with a hard drive, you can often hear quiet grinding, clicking and whirring sounds as this happens (if they are loud, time to take action!)


An example of a failing hard drive

Because this process is mechanical, after some years of use, the mechanisms can start to wear out (like our poor friend in the figure above). In more dramatic cases, this can mean sudden failure. But more likely is something called “bad sectors”. This is where tiny portions of the drive are damaged - either physically or logically. Physical damage can’t be repaired, and logical damage can - for a deeper dive into this, have a look here .

When a drive detects these bad sectors, the software running on the logic board will mark them as unusable, making sure that no information is written to them. A hard disk drive can continue to function with a handful of bad sectors, but once they appear it is a sign the drive will likely fail imminently and should be replaced. Eventually, if a drive has enough unrectified bad sectors, it will stop working entirely.


Nobody's favourite screen

Something that can contribute to bad sectors is forcing the computer to turn off due to impatience - this can become a vicious cycle. As the computer gets slower, the likelihood that the user will give up and force it to turn off or reboot increases - this is a very bad idea - if you don’t shutdown or reboot your computer properly, it’s likely you will interrupt the mechanics of the hard drive while it is in the middle of something. Whilst hard drives are moderately tolerant of this, in the long term there is no doubt that it will damage the hard drive if the computer is forced to power off or reboot unexpectedly. (Incidentally, you shouldn’t do this on any computer, even one with an SSD, unless you absolutely have to because it has crashed - the likelihood of freezes and crashes significantly reduces with SSDs however, as they are so much faster and more efficient than their older predecessors.)

Usually, when a client presents a computer to me that is running slowly, I will check the drive for these bad sectors with some diagnostic software. Quite often, especially if it is an older machine, there will be some present and the drive will need replacing.

However, even if a hard disk drive has no bad sectors and is running exactly as intended, it simply cannot match the speeds offered by SSDs.



Solid State Drives - The Speed Demon


Inside a Hard Disk Drive and a Solid State Drive

SSDs are built on the same technological principle as hard drives, but the execution is different. Rather than platters, SSDs store information on NAND flash memory  - these are essentially digital chips with no moving parts. NAND flash memory is the same technology that the SD cards used by digital cameras and mobile phones. However, the NAND flash memory used in SSDs is a lot more durable than that found in SD cards - and a lot faster. In the early days of SSDs, they were very expensive, and care had to be taken to limit how much information you wrote to them, as they were nowhere near as durable as hard drives. However, over time the technology used has been improved - these days you can confidently use them in most desktops and laptops as a drop in replacement for hard drives.

While prices have fallen, SSDs still cost about twice as much per gigabyte (GB) as hard drives, so if you need a lot of storage, the best thing to do is have an SSD on which you install your operating system (Windows, MacOS or Linux) and a second large hard disk to store high capacity files such as photos, videos and music. This is easy on a desktop machine, as they often have a lot of space. On laptops it can be trickier - very few have space for more than one drive, although if you can sacrifice your CD/DVD drive, it’s possible to get converter caddies  which allow you to use the space for the DVD drive as an additional hard drive bay. However, most laptops have a slower SATA-II speed connector for the DVD drive, as DVDs don’t require that much speed. SATA-II is limited to a speed of 300 MB/s, and given that most SSDs are capable of more than that (as we will see in Part 2 ), it’s much better to put an SSD in the original hard drive slot, and use the converter caddy for a hard drive.



So, what difference does an SSD really make?



Well, take a look above. The first column is an NVMe SSD and the second column is a SATA SSD (we will cover the difference between these in Part 2 ). The third column is a hybrid SSD/hard drive (which aren’t really much faster than a hard disk drive - there is a small NAND flash chip that caches frequently used data but this doesn’t really translate to a huge speed boost in real-life), and finally the fourth column is a hard disk drive.

As you can see, the machines with SSDs boot up, and are ready to use, much more quickly than the machines without them. This speed increase will also be felt when you load programs. It makes a machine that was previously running slowly seem like new. Also, because there are no moving mechanical parts in SSDs, they are a lot more physically durable - perfect for laptops that frequently get thrown in and out of bags etc.

This doesn’t mean that SSDs can’t get bad sectors, it just means that mechanical wear is almost impossible as there are no moving parts. Instead, what you have to look out for is a drive’s Terabytes Written (TBW)  rating. This is an indication from the manufacturer of how much data they expect can be written to the drive in it’s lifetime. This number is usually very high, and the average user can expect to get at least 3-5 years life out of an SSD (and probably longer than that) - this is usually the level of warranty you receive from the manufacturer. Of course, nothing is guaranteed, so it’s vital to keep good backups (look out for a future blog post about this!)

If I’ve convinced you, it’s time to move on to SSDs - Part 2 - Okay, which one do I need?

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