What are Solid-State Drives
A Solid-State Drive is made from flash memory. Essentially these are microchips that store data that is not lost if the power is switched off. Since it is flash memory, it has no moving parts. This makes them a bit more resilient to force from them being dropped than a hard disk would be. However, I would not drop them or apply force on them. They can still be broken.
Solid-State Drives have no moving parts. Since they don’t have a motor in them as hard disks do, they use less power. Since they don’t have any moving parts, they don’t have parts like motors that wear out due to movement. However, as we will see, Solid-State Drives do wear out.
Solid-State Drives are much faster than hard disks. Modern flash memory can read sequential data a lot faster than hard disks can in most circumstances. This is especially true for high-performance Solid-State Drives. Random access of data is faster, since with hard disks the head of the hard disk has to move where the data is. Solid-State Drives have no head to move and also can read multiple chips at the same time.
The only real downside to Solid-State Drives is that generally they cost more than hard disks for the same capacity. I say generally because, with hard disks there is a higher base cost than with Solid-State Drives. That is, the hard disk spindle and other components cost a lot more than the components required to make a Solid-State Drive. Thus, if you are looking for the cheapest storage devices on the market and not concerned about the capacity, you will find Solid-State Drives are the cheapest. Once you start moving up the price range, hard disks take over since you can store a lot more on them once the manufacturer recovers the base cost.
Since hard disks have moving parts, they are subject to components wearing out and failing. Solid-State Drives don’t have this problem since they have no moving parts, however they still wear out.
Solid-State Wearing
In the case of Solid-State Drives, writing to the flash cells causes wear to those cells. Essentially, the cells are rated to be written to a number of times before the cell will fail. It is like writing on a piece of paper with a pencil. If you later change what you wrote, you would use an eraser to remove the pencil marks from the paper. Each time you do this, it wears down the paper until it tears, and then you can’t use it anymore.
Wear Leveling
Solid-State Drives use wear leveling to prolong the life of the flash memory. Think of it like a tire on your car. If the tire gets badly damaged in one place you need to replace the whole tire. Once a flash cell reaches its write limit, the drive will start using a small amount of reserve blocks. When all the reserve blocks are used, you really need to replace the Solid-State Drive, as it is only a matter of time before you lose data or have a failure.
The lowest writeable unit on a Solid-State Drive is a block. Thus, technically, the cell does not reach the write limit, the block reaches its write limit, but you get the idea. Some backup blocks are available for replacement of a block that has reached its write limit, however, once these are gone the device should not be used.
To understand how wear leveling works, let’s consider a Solid-State Drive without wear leveling. Without wear leveling, certain blocks in the Solid-State Drive will get used more than others. Operating systems will write to certain blocks all the time. For example, the page file is always written to the same location. Without wear leveling, the same blocks on the Solid-State Drive get written to all the time. Therefore, wear is concentrated to certain blocks and not spread out. Some blocks will not be used much, while others will be written to excessively, which will reduce the life span of the Solid-State Drive.
Wear leveling fixes these problems by evening out the wear. In order to do this, a block that is written to a lot will be moved to a different location that has been written to less. Thus, it evens out the wear across the whole device.
The wear leveling should mean the wear on the drive is pretty even, thereby extending the lifespan of the Solid-State Drive. Modern Solid-State Drives all use wear leveling. Only the very first Solid-State Drives did not have wearing leveling and would therefore wear out very quickly.
You don’t need to worry about wear leveling since it is all done in the background for you. But it is worth knowing what it is and how to check how much life is left in your Solid-State Drive.
CrystalDiskInfo
CrystalDiskInfo is a free tool that can read statistics and information from your drive. This computer has two Solid-State Drives installed. You can see there is a lot of information at the bottom. However, this information differs from device to device. There is no standard for this information, thus different devices will give you different information. Some devices will provide more than others and some devices may record data where others do not. So, if you see a zero value it may be zero or it may be the device does not record that information.
Notice at the top left, the health status of the device is reported as 99%. So essentially, one percent of the life of this device has been used. The manufacturer of the device may also provide tools which give you information about the device and how much life it has left.
On the right-hand side, you will notice the number of writes written to the solid-State Drive is listed. Although this is useful, you need to know how many writes the device can support before it fails. So generally, I would just look at the status of the device.
I will change to my other Solid-State Drive. You will notice that this Solid-State Drive gives less information than the other one. What information you get will depend on what the manufacturer of the device decides to give you.
With this Solid-State Drive, the life expectancy is 93%, so there is still a lot of life left in the drive. Although wear leveling is done for you, there is something you can do to increase the life of your Solid-State Drive.
Leave Some Free Space
To increase the lifespan of the Solid-State Drive, you want to reduce the number of writes on that drive. One way to achieve this is to leave some free space on the Solid-State Drive. Leaving some free space allows for more efficient storage of the data.
Opinions vary on how much space you should leave; I have seen ranges from 25% to 10%. Let’s have a look at why it is important.
In this example, I have shown a small area of a very full Solid-State Drive. Solid-State Drives store data in blocks. However, these blocks are divided up into pages. The free pages are shown in green, and the used pages are gray. This is a simple example where each block has four pages. Different Solid-State Drives may have a different number of pages per block – 128 pages per block is a common size for Solid-State Drives.
When data in a page is changed, the block needs to be read, the changes applied and the block rewritten with the new changes. So, let’s consider what happens when we attempt to write three pages to the Solid-State Drive.
In this case, there are three pages on the Solid-State Drive that have data that needs to be changed. Thus, to write the three pages, each block needs to be read, the new page added to the block and then the whole block rewritten. In order for this to occur, three reads and three writes need to be completed. Since there are no free blocks this is the only way we can update the pages.
Now let’s consider that on the Solid-State Drive there is a free block. When the pages are written, since the block is empty, only one write is required to write the three pages. All the pages that need to be updated can all be written to the same block.
Thus, you can see that if there is free space on the Solid-State Drive, this increases its efficiency. Essentially, if there is free space, this reduces the number of reads and writes that need to be done. There is also another feature that is used to reduce wear of the Solid-State Drive.
Trim
Solid-State Drives also use a feature called Trim. Trim commands are sent by the operating system to tell the Solid-State Drive what data is not needed. Let’s consider that we have two different blocks on a Solid-State Drive.
These blocks contain pages in green that are free and pages that have been used in gray. There are 11 used pages between the two blocks, thus the data can’t be placed in a single block.
When Trim is run, the operating system informs the Solid-State Drive what pages are no longer required. When the operating system deletes a file, it marks the file as deleted, however, the Solid-State Drive does not know the data is no longer required. Thus, Trim informs it that this data is no longer required.
Solid-State Drives will perform housekeeping in the background. In this case, the Solid-State Drive, because Trim has been run, knows what pages are no longer required. Therefore, the housekeeping function can combine the two blocks into one. Performing this kind of reorganization makes future storing of data more efficient. Even if the housekeeping is not run, knowing which pages are no longer required makes other functions more efficient. That is, data that is no longer required does not need to be read from or rewritten to the device.
Modern operating systems support Trim. Running Trim reduces writes and thus increases the lifespan of Solid-State Drives. In older operating systems, Trim can be run manually using the manufacturer’s tools. However, don’t run it too often. Running Trim makes changes to the Solid-State Drive and thus writes are performed. Operating Systems like Windows run Trim only once a week. If you run Trim too often, you end up wearing out the Solid-State Drive faster than if you did not run it at all.
SSD and Hard Disk Use
Generally speaking, nowadays the boot drive will be a Solid-State Drive. Solid-State Drives compared with hard disks have faster random access. Using them to boot your drive and run your operating system will make it run a lot faster. You will notice the computer booting up faster and being more responsive when doing things like opening the start menu, for example.
Nowadays, smaller Solid-State Drives are cheaper than hard disks. This is because the base cost of a hard disk is more than a Solid-State Drive. So, you will find that 128 Gigabyte and 256 Gigabyte Solid-State Drives are generally cheaper than the cheapest hard disk. The smallest hard disks tend to be around the one Terabyte mark, as it becomes financially unviable to make them with small capacity. In the case of laptops, the majority of manufacturers no longer use hard disks.
When it comes to hard disks, capacity is still king. For large storage capacity, you can’t beat hard disks for the price. So generally, I would get the largest Solid-State Drive my budget allows for the boot drive and then purchase a hard disk for additional storage if I needed it. You will find that if the user does not have a need to store a lot of data on the computer, nowadays they will probably just have a single Solid-State Drive to run their operating system and store their data files.
Now let’s have a look at the different interfaces Solid-State Drives come with.
Interface
There are a number of different Solid-State interfaces. The newest type is M.2 NVMe. M.2 is a newer standard for storage. Essentially, it is a rectangular circuit board with an edge connector. NVMe stands for Non-Volatile Memory Express. Non-Volatile Memory simply means the data is not lost if the power is lost – the Express part just refers to the fact that it is using the PCI Express bus.
The M.2 standard can be used for other devices, for example, a Wi-Fi adapter. To determine what the M.2 device is designed to work with, there is a notch missing in the edge connector. In the case of Solid-State Drives, if there is one notch missing it is using PCI Express – this is known as M Key.
NVMe was released in 2012. Thus, unless you have an old computer it should be supported. Since it uses PCI Express it is very fast. It also uses a newer protocol. Given that older protocols were designed for spinning hard disks using a motor, the newer protocol is designed with Solid-State Drives in mind.
The previous standard was the M.2 SATA standard. This standard uses the SATA protocol. Essentially, it is the same as a SATA storage device with a different connector. Since it uses the SATA protocol, it has a maximum speed of 6 Gigabits per second. With the increasing speed of flash memory, 6 Gigabits per second became a bottle neck for Solid-State Drives, thus the need for a faster standard like NVMe. Therefore, you may find that M.2 SATA storage is slowly disappearing from the market. Most of the M.2 Solid-State Drives currently on the market are NVMe.
M.2 SATA has two notches. The right one is the SATA notch identifying the storage as SATA. The other notch is missing so that it can also be used in a PCI Express connector. This is known as B plus M Key. The right notch is the B Key and the left notch is M Key.
I have an adapter that has two connectors, one for SATA and one for PCI Express. I also have two M.2 SSDs. One is SATA and the other is NVMe. The SATA SSD has two notches. The NVMe SSD has one notch.
This adapter has the same connectors as your motherboard would have. Notice the connectors are keyed. The key is essentially a plastic protrusion that prevents the wrong SSD being plugged into the connector or the SSD being plugged in upside down.
Notice that the SATA SSD will plug in the SATA connector as expected. If your motherboard has this connector, it will support SATA SSDs, however, if not it will be PCI Express.
You will notice that because the SATA SDD has two notches, it will plug into the NVMe connector as well. On older motherboards the PCI Express connectors supported SATA and NVMe SSD. However, you will find that new motherboards may have connectors that only support NVMe. So, if you plug in a SATA SSD and you find it is not working, it may be because the connector does not support it. Check your motherboard manual, and you may find that some connectors support SATA and some do not.
I will now plug in the NVMe SSD. Notice that this plugs into the NVMe connector, which is to be expected. Notice that I won’t be able to plug it into the SATA connector. The keying is different and thus, it won’t go into the connector.
When purchasing M.2 devices, make sure your adapter matches the connector. For storage devices, the B key and M key will be used. Other devices like network devices use different keying which I have not covered in this video. But essentially different keying just means the protrusion is in a different position.
The next connector that I will look at is the SATA connector. This connector is limited to a maximum speed of 6 Gigabits per second. With the increased speed of flash memory this has become too slow. The newest version of SATA is version 3, however, we are unlikely to see a version 4 of SATA due to engineering limitations. Thus, it appears that SATA will never go above this maximum speed.
SATA is fast enough for hard disks but not Solid-State Drives. Thus, you will probably see SATA still used for hard disks, but M.2 taking over for Solid-State Drives.
The last type I will look at is mSATA, which stands for mini-SATA. Essentially, feature wise it is the same as SATA, however, it just uses a different connector. I am a bit surprised that CompTIA still has this as an exam objective as it had a limited market share. Nowadays, it has been replaced by M.2. It essentially had some use in laptops but did not really take off. Unless you are working with an old laptop, you won’t come across it.
End Screen
That concludes this video from ITFreeTraining on Solid-State Drives. I hope this video has helped you understand how they work and how to use them. Until the next video from us, I would like to thank you for watching.
References
“The Official CompTIA A+ Core Study Guide (Exam 220-1101)” pages 53 to 55
“Mike Myers All in One A+ Certification Exam Guide 220-1101 & 220-1102” pages 275 to 280
“Picture: Flash Drive” https://en.wikipedia.org/wiki/Flash_memory#/media/File:USB_flash_drive.JPG
Credits
Trainer: Austin Mason http://ITFreeTraining.com
Quality Assurance: Brett Batson http://www.pbb-proofreading.uk
