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Solid State Drives (SSD's) explained - NEW 2023 edition!
What are SSD's?
SSD's are harddrives made out of memory chips which are controlled by a controller. Traditional harddrives use magnetic disks that rotate whilst the heads read and write to and from it, this can take time for the harddrive to spin up and seek to the correct part of the disk, this is also known as seek time. Seek times on SSD's are incredibly low due to there are no moving parts. Data is transmitted from memory chips to the controller then to the pc.
MLC Vs SLC Vs TLC Vs QLC (Multi-Level Cell Vs Single-Level Cell Vs Triple-Level Cell Vs Quad-Level-Cell)
MLC flash has four possible states per cell, so it can store two bits of information per cell. Due to this, it is not as durable as SLC NAND flash. MLC flash usually has a lifespan of 10,000-30,000 cycles.
TLC SSD's are available from Samsung and Sandisk. TLC stores 3 bits of data per cell. It is cheaper to manufacture than SLC or MLC but it is difficult to make a controller work well with it. Silicon motion has recently announced a new controller that will work with TLC memory so expect TLC to become available from many manufacturers soon rather than just samsung and sandisk. TLC memory has a lifespan of 1,000-5,000 cycles. More info: http://www.anandtech.com/show/9165/...-reference-design-ssd-review-tlc-for-everyone
SLC stands for Single-Level-Cell. SLC flash only stores 1 bit of data per cell, but this allows the cell to last much longer than MLC flash. SLC flash is usually faster than MLC, but because it does not store as much data, it is more expensive to create a drive of equivalent capacity to an MLC drive. SLC flash usually has a lifespan of 100,000 to 2,000,000 cycles. For more information read: http://www.supertalent.com/datasheets/SLC_vs_MLC whitepaper.pdf
QLC stands for Quad-Level-Cell stores 4 bits of data per cell. It is cheaper per gigabyte but has a lower lifespan.
more info: https://en.wikipedia.org/wiki/Multi-level_cell
Lifespan
The lifespan of an SSD is determined by the number of cycles per block of memory and how much you use it. Reading from an SSD does not use up cycles, but writing does. All MLC drives should last at least 5 years of normal usage, with SLC drives lasting much longer. However, other factors, such as wear levelling and write amplification can have an impact on lifespan, and it is possible for a high quality MLC drive to last longer than a low quality SLC SSD.
For example, Intel's 730 Series SSD's are MLC, and they are rated to last for 70GB of writes every day, for 5 years. No home user would write that amount, so an Intel SSD is likely to last many years longer than the 5yrs warranty.
Durability
SSD's are incredibly durable because they contain no moving parts, unlike a mechanical hard drive. Also, because SSD's do not store data using magnetism, they are less likely to be affected by magnets, meaning the only way to break an SSD is to physically break it. SSD's are rated at up to 1500G shock before damage.
Power
Older SSD's used to use a lot of power when idle so sometimes they used more power than mechanical hard drives. New SSD's use 20-95mW when idle. When in active use some SSD's can use more power than some low-power mechanical hard drives such as 5400rpm drives however in the overwhelming majority of instances SSD's will use less power when actively reading or writing. Modern sata SSD's typically use 2-3.5w when actively reading or writing, mechanical hard drives tend to use 6-9w when actively reading or writing for 3.5" hard drives, 2.5" 5400rpm hard drive can use as little as 3w when reading and writing. Some M.2 Pci-E ssd's can use over 8 watts. Due to your hard drive not actively reading and writing most of the time such as when you are reading a webpage the power consumption of an SSD is usually 90% lower than a mechanical hard drive.
SSD's can use as little as 2mW in SATA Device Sleep mode (DevSlp) (the amount of power that the ssd uses when you computer send a signal to the ssd to put it into an ultra low power sleep mode). Modern ssd's usually use 20-95mW in 'Slumber sleep mode'.
More info about SATA power: https://www.sata-io.org/power-management
Benefits
The benefits of using an SSD over a conventional HDD are huge. They offer higher read and write speeds, smaller form factor than desktop HDD's, much faster access times, they are silent and produce little heat.
Read and write speeds are higher than an HDD simply due to the fact they use NAND flash memory. A mechanical HDD is limited by the speed it can spin at, and the faster they spin, the more noise and heat is produced. New 2.5" SSD's usually offer between 450MB/s and 560MB/s (limited by SATA 6GBps a.ka sata3), giving them great performance when opening large programs. Modern M.2 Pci-E ssds can offer over 12,000MB/s
Currently, many consumer SSD's come in the 2.5" form factor, the rest are mostly m.2 pci-e. They are both smaller than 3.5" HDD, allowing several drives to fit in the same amount of space.
Access times on new SSD's are under 0.1ms. A regular 3.5" 7200rpm hard drive takes 12ms+, this is exceptional, and makes them brilliant for an operating system and software.
These are ideal for games, levels and maps will load incredibly quickly compared to standard hard drives. Installing software that has large numbers of small files will install much faster too e.g .NET framework, Java JRE, Libreoffice and other common installers. Files in 'file explorer' display almost instantly.
SSD Controllers
Jmicron were the first manufacturer to create controllers for SSD's, they started off at very low speeds of approx 50MB/s read and 30MB/s write which was slower than the mechanical drives available at that time. The Jmicron controller JMF601A/602A used in the OCZ Core v1 SSD's suffered from stuttering problems, sometimes 3 seconds of the system stalling due to the poor controller and lack of cache memory. New SSDs do not have these problems.
List of SSD controller manufacturers: https://en.wikipedia.org/wiki/List_of_flash_memory_controller_manufacturers
TRIM command
The TRIM command is needed as SSD's lose significant performance over time due to poor command structuring to read and erase blocks on the memory chips, this is built-in to modern operating systems.
for more in depth information read:
http://windowsitpro.com/windowsnt20...-in-write-performance-as-theyre-used-why.html
http://windowsitpro.com/article/art...state-disks-ssds-and-why-is-it-important.html
Which drives support TRIM command
All modern SSD's support the TRIM command, some older SSD's don't, some do with a firmware update.
What Software/Firmware and Operating System do i need for the TRIM command to work?
Windows 7 and newer have the TRIM command built-in, users just need the SSD's to have a new firmware that has TRIM support flashed onto the SSD for it to work and windows 7 and newer will take care of it for you automatically. All drives since ~2012 have TRIM built-in.
Firmware Updates
A small number of older SSD's were updated via a mini-usb connection on the SSD and upgraded via another pc using the provided mini-usb to usb cable. Modern SSD's use a DOS-based firmware updater or a windows-based firmware updater. If you use a dos-based updater you will likely need to burn a bootable cd-r/dvd-r or make a usb stick bootable. To find out how to upgrade the firmware for each brand of SSD see here: http://www.storagereview.com/how_upgrade_ssd_firmware
Raid 0
Raiding SSD's will result in much faster sustained transfer rates, 2 drives can be up to 2x as fast and 3 drives can be up to 3x as fast. SSD's have slower latency when you raided them together as shown in this raid0 SSD review: http://www.tomshardware.co.uk/ssd-raid-benchmark,review-32689.html. As a result starting windows, shutting down windows and starting applications will be slower. Most users wont notice much difference in raiding as good SATA SSD's already have 560mb/s+ read and write for sata SSDs or even faster with M.2 Pci-E drives so there isn't any point doing that.
TRIM will NOT work in Raid0 for some SSD's, motherboard raid controllers and 3rd party raid controllers. If you need to use raid you should check the SSD and motherboard before buying or 3rd party raid card if you aren't using the motherboard's built-in raid, more info: https://en.wikipedia.org/wiki/Trim_(computing)
Can i use an SSD for an external usb/esata harddrive or in a PS3 games console?
Yes. You can put a 2.5" SATA SSD in an external SATA usb hard drive caddy and use it as an external hard drive. You can also buy external SSD hard drives without having to do this yourself. Yes, you can use an SSD in a ps3 games console instead of the mechanical hard drive, game installation times and game loads times can be quite a lot faster, gaming itself however will not benefit from this.
Which SSD's to buy?
Early versions of SSD's gave poor performance and some had stuttering write problems, avoid really old SSD's like the plague. Most SSD's manufactured from 2011 onwards should have little to no problems if you update the firmware to the latest version. ADATA ssd's are known for being unreliable, stay clear from these.
NvME vs AHCI:
'Non-Volatile Memory Express' vs 'Advanced Host Controller Interface'. AHCI was created by Intel for SATA mechanical hard drives. The specification describes a system memory structure for computer hardware vendors to exchange data between host system memory and attached storage devices. This was included in windows vista, more info: https://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface
NVM Express, NVMe, or Non-Volatile Memory Host Controller Interface Specification (NVMHCI), is a specification for accessing solid-state drives (SSDs) attached through the PCI Express (PCIe) bus. more info: https://en.wikipedia.org/wiki/NVM_Express
The NVMe device interface has been designed from the ground up, capitalizing on the low latency and parallelism of PCI Express SSDs, and complementing the parallelism of contemporary CPUs, platforms and applications.
The first NvME drive drive released was a Samsung enterprise drive in 2013.
Microsoft added native support for NVMe to Windows 8.1 and Windows Server 2012 R2. Native drivers for Windows 7 and Windows Server 2008 R2 have been added in updates. Linux kernel 3.3 added support for NvME. MacOS 10.10.3 added support for NvME.
What are mSATA, SATA Express, M.2, U.2 and U.3?:
M.2 (formerly known as NGFF a.k.a Next Generation Form Factor). Image of an M.2 SSD:
mSATA is 30mm wide and 50.95mm long, this standard is no longer used. M.2 is 22mm wide and the length is one of the following: 30mm, 42mm, 60mm, 80mm or 110mm.
More info about M.2: https://www.sata-io.org/sata-m2-card
M.2 can either be used with the SATA bus or the PCI-E bus. SATA will limit it to 6Gbps (real world speed of 560MB/s), you can buy M.2 PCI-E drives that offer up to 12,000MB/s real world real speeds as of April 2023. The M.2 specification provides four PCI Express lanes and one SATA 6Gbps port, exposed through the same connector, allowing use of both PCI Express and SATA storage devices in form of M.2 cards. Exposed PCI Express lanes provide a pure PCI Express connection to the storage device, without any additional layers of bus abstraction.
U.2 (formerly known as SFF-8639) More info about U.2: http://www.anandtech.com/show/9363/sff8639-connector-renamed-as-u2
U.3 is a newer enterprise ssd standard.
SATA Express was a newer standard that failed to catch on, instead M.2 caught on.
SSD speeds:
Current 2.5" SATA SSD's max out at approximately 560MB/s sustained read and write speeds. The random read/write speeds for SATA 6Gbps SSD's is a maximum of 100,000 iops read and write. These iops and max read/write speeds are the maximum that the SATA 6Gbps bus can cope with. Iops is the number of input and output operations per second, it is used frequently to compare the real-world speeds of SSD's when transferring lots of small files such as when used as a web server or database server.
Nand vs V-Nand vs 3D-Nand and nanometer processes:
Producing memory below 20nm in size became very difficult as errors are much more common at low nanometer process sizes. As a result you need a good quality controller to be able to detect these errors and allocate portions of the SSD to use instead of the faulty portions detected. Lower nm processes require huge investment and often produce low yields for quite some time until the problems have been fixed. As a result of the errors that occur and the large investment required, memory manufacturers are moving to 3D nand flash memory instead which is usually made in a large well established high yield nanometer processes. This involves stacking the memory circuits on top of each other, chips will use up to 172 layers which will lead to lower cost and and lower power consumption.
Are SSD's good for servers and datacentres and are there different types for those?:
YES! However if you are planning to use an SSD for a business server such as a web server, database server etc then you should buy a datacentre specific SSD which often have 'DC' in the model name. Datacentre SSD's are not the same as consumer SSD's, they are optimised for sustained write speeds rather than maximum speed. One of the reasons is because the processor on the SSD can get quite warm if you were to write data constantly at full speed for several minutes. More info: http://www.anandtech.com/show/9396/samsung-sm951-nvme-256gb-pcie-ssd-review/3 Non-datacentre SSD's used for such purposes can be multiple times slower when used for this purpose so make sure you buy a datacentre-specific SSD (preferably Intel) if you are planning on using an SSD for such purposes.
Over-provisioning:
This is whereby the memory chips on your SSD are larger than the capacity you are able to use. For example you may have an SSD with 512GB worth of nand memory chips but the SSD is sold to you as as 480GB drive. This is because SSD memory sectors can become faulty, as a result the SSD keeps some sectors as spare that it can re-allocate when it notices some faulty sectors. SSD's used to require a very significant amount of over-provisioning in the first few years, but now they usually use less than 10% due to better error checking algorithms.
What is an 'SSHD' a.k.a 'Hybrid SSD'?:
A hybrid SSD was a regular mechanical hard drive with some nand flash memory inside too. These never became popular: https://en.wikipedia.org/wiki/Hybrid_drive http://www.intel.com/content/dam/ww...gy-briefs/smart-response-technology-brief.pdf
Data corruption and retention:
Data corruption can occur if there is a loss of power: http://www.infoworld.com/article/26...risk-massive-data-loss--researchers-warn.html http://www.zdnet.com/article/how-ssd-power-faults-scramble-your-data/
Data can be retained for 1yr or longer without power being connected to an SSD if the room temperature is 30c or lower. If the room temperature is 55c or higher the data may only be retained for 7 days or more. So make sure you keep the psu on your desktop switched on so that a trickle of power is sent to your SSD. If you are using a laptop make sure the power cord is connected or that a battery with some charge is connected and this won't be a problem, more info:http://www.anandtech.com/show/9248/the-truth-about-ssd-data-retention
DRAM-less SSD's:
Manufacturers started making SSD controllers without the need to use LPDDR2 or newer memory several years ago, these require less chips, use less power and are won't lose data in the event of a power failure, LPDDR2 memory is volatile, nand is not. The downside to getting rid of LPDDR2 memory is that the performance is reduced. This is why these controllers will be used only in low-end SSD's in order to reduce cost.
File Systems:
SSD's can be formatted with a variety of file systems such as NTFS, EXT4, BTRFS etc. Samsung has created a new file system specifically designed for flash memory called F2FS (flash-friendly file system). F2FS is open source and patent-free and is available on linux and android. Samsung's own mobile devices already use F2FS with android, so do many Motorola mobile devices. More info: https://en.wikipedia.org/wiki/F2FS
Why are larger capacity SSD's often faster than smaller ones?:
The reason that smaller drives are often slower is that the speed of each individual memory chip is usually not the speed that the drive is rated for. The controller allows the chips to work together to combine the speed of the chips together resulting in faster speed. Smaller capacity drives have fewer memory chips therefore sometimes the combined speed of the chips isn't is fast as with higher capacity drives. This problem has greatly reduced over the past few years as the speed of each individual chip has increased due to the use of 3d-nand flash chips.
Here is a great SSD program to give you information about your ssd:
CrystalDiskInfo: http://crystalmark.info/download/index-e.html
What are SSD's?
SSD's are harddrives made out of memory chips which are controlled by a controller. Traditional harddrives use magnetic disks that rotate whilst the heads read and write to and from it, this can take time for the harddrive to spin up and seek to the correct part of the disk, this is also known as seek time. Seek times on SSD's are incredibly low due to there are no moving parts. Data is transmitted from memory chips to the controller then to the pc.
MLC Vs SLC Vs TLC Vs QLC (Multi-Level Cell Vs Single-Level Cell Vs Triple-Level Cell Vs Quad-Level-Cell)
MLC flash has four possible states per cell, so it can store two bits of information per cell. Due to this, it is not as durable as SLC NAND flash. MLC flash usually has a lifespan of 10,000-30,000 cycles.
TLC SSD's are available from Samsung and Sandisk. TLC stores 3 bits of data per cell. It is cheaper to manufacture than SLC or MLC but it is difficult to make a controller work well with it. Silicon motion has recently announced a new controller that will work with TLC memory so expect TLC to become available from many manufacturers soon rather than just samsung and sandisk. TLC memory has a lifespan of 1,000-5,000 cycles. More info: http://www.anandtech.com/show/9165/...-reference-design-ssd-review-tlc-for-everyone
SLC stands for Single-Level-Cell. SLC flash only stores 1 bit of data per cell, but this allows the cell to last much longer than MLC flash. SLC flash is usually faster than MLC, but because it does not store as much data, it is more expensive to create a drive of equivalent capacity to an MLC drive. SLC flash usually has a lifespan of 100,000 to 2,000,000 cycles. For more information read: http://www.supertalent.com/datasheets/SLC_vs_MLC whitepaper.pdf
QLC stands for Quad-Level-Cell stores 4 bits of data per cell. It is cheaper per gigabyte but has a lower lifespan.
more info: https://en.wikipedia.org/wiki/Multi-level_cell
Lifespan
The lifespan of an SSD is determined by the number of cycles per block of memory and how much you use it. Reading from an SSD does not use up cycles, but writing does. All MLC drives should last at least 5 years of normal usage, with SLC drives lasting much longer. However, other factors, such as wear levelling and write amplification can have an impact on lifespan, and it is possible for a high quality MLC drive to last longer than a low quality SLC SSD.
For example, Intel's 730 Series SSD's are MLC, and they are rated to last for 70GB of writes every day, for 5 years. No home user would write that amount, so an Intel SSD is likely to last many years longer than the 5yrs warranty.
Durability
SSD's are incredibly durable because they contain no moving parts, unlike a mechanical hard drive. Also, because SSD's do not store data using magnetism, they are less likely to be affected by magnets, meaning the only way to break an SSD is to physically break it. SSD's are rated at up to 1500G shock before damage.
Power
Older SSD's used to use a lot of power when idle so sometimes they used more power than mechanical hard drives. New SSD's use 20-95mW when idle. When in active use some SSD's can use more power than some low-power mechanical hard drives such as 5400rpm drives however in the overwhelming majority of instances SSD's will use less power when actively reading or writing. Modern sata SSD's typically use 2-3.5w when actively reading or writing, mechanical hard drives tend to use 6-9w when actively reading or writing for 3.5" hard drives, 2.5" 5400rpm hard drive can use as little as 3w when reading and writing. Some M.2 Pci-E ssd's can use over 8 watts. Due to your hard drive not actively reading and writing most of the time such as when you are reading a webpage the power consumption of an SSD is usually 90% lower than a mechanical hard drive.
SSD's can use as little as 2mW in SATA Device Sleep mode (DevSlp) (the amount of power that the ssd uses when you computer send a signal to the ssd to put it into an ultra low power sleep mode). Modern ssd's usually use 20-95mW in 'Slumber sleep mode'.
More info about SATA power: https://www.sata-io.org/power-management
Benefits
The benefits of using an SSD over a conventional HDD are huge. They offer higher read and write speeds, smaller form factor than desktop HDD's, much faster access times, they are silent and produce little heat.
Read and write speeds are higher than an HDD simply due to the fact they use NAND flash memory. A mechanical HDD is limited by the speed it can spin at, and the faster they spin, the more noise and heat is produced. New 2.5" SSD's usually offer between 450MB/s and 560MB/s (limited by SATA 6GBps a.ka sata3), giving them great performance when opening large programs. Modern M.2 Pci-E ssds can offer over 12,000MB/s
Currently, many consumer SSD's come in the 2.5" form factor, the rest are mostly m.2 pci-e. They are both smaller than 3.5" HDD, allowing several drives to fit in the same amount of space.
Access times on new SSD's are under 0.1ms. A regular 3.5" 7200rpm hard drive takes 12ms+, this is exceptional, and makes them brilliant for an operating system and software.
These are ideal for games, levels and maps will load incredibly quickly compared to standard hard drives. Installing software that has large numbers of small files will install much faster too e.g .NET framework, Java JRE, Libreoffice and other common installers. Files in 'file explorer' display almost instantly.
SSD Controllers
Jmicron were the first manufacturer to create controllers for SSD's, they started off at very low speeds of approx 50MB/s read and 30MB/s write which was slower than the mechanical drives available at that time. The Jmicron controller JMF601A/602A used in the OCZ Core v1 SSD's suffered from stuttering problems, sometimes 3 seconds of the system stalling due to the poor controller and lack of cache memory. New SSDs do not have these problems.
List of SSD controller manufacturers: https://en.wikipedia.org/wiki/List_of_flash_memory_controller_manufacturers
TRIM command
The TRIM command is needed as SSD's lose significant performance over time due to poor command structuring to read and erase blocks on the memory chips, this is built-in to modern operating systems.
for more in depth information read:
http://windowsitpro.com/windowsnt20...-in-write-performance-as-theyre-used-why.html
http://windowsitpro.com/article/art...state-disks-ssds-and-why-is-it-important.html
Which drives support TRIM command
All modern SSD's support the TRIM command, some older SSD's don't, some do with a firmware update.
What Software/Firmware and Operating System do i need for the TRIM command to work?
Windows 7 and newer have the TRIM command built-in, users just need the SSD's to have a new firmware that has TRIM support flashed onto the SSD for it to work and windows 7 and newer will take care of it for you automatically. All drives since ~2012 have TRIM built-in.
Firmware Updates
A small number of older SSD's were updated via a mini-usb connection on the SSD and upgraded via another pc using the provided mini-usb to usb cable. Modern SSD's use a DOS-based firmware updater or a windows-based firmware updater. If you use a dos-based updater you will likely need to burn a bootable cd-r/dvd-r or make a usb stick bootable. To find out how to upgrade the firmware for each brand of SSD see here: http://www.storagereview.com/how_upgrade_ssd_firmware
Raid 0
Raiding SSD's will result in much faster sustained transfer rates, 2 drives can be up to 2x as fast and 3 drives can be up to 3x as fast. SSD's have slower latency when you raided them together as shown in this raid0 SSD review: http://www.tomshardware.co.uk/ssd-raid-benchmark,review-32689.html. As a result starting windows, shutting down windows and starting applications will be slower. Most users wont notice much difference in raiding as good SATA SSD's already have 560mb/s+ read and write for sata SSDs or even faster with M.2 Pci-E drives so there isn't any point doing that.
TRIM will NOT work in Raid0 for some SSD's, motherboard raid controllers and 3rd party raid controllers. If you need to use raid you should check the SSD and motherboard before buying or 3rd party raid card if you aren't using the motherboard's built-in raid, more info: https://en.wikipedia.org/wiki/Trim_(computing)
Can i use an SSD for an external usb/esata harddrive or in a PS3 games console?
Yes. You can put a 2.5" SATA SSD in an external SATA usb hard drive caddy and use it as an external hard drive. You can also buy external SSD hard drives without having to do this yourself. Yes, you can use an SSD in a ps3 games console instead of the mechanical hard drive, game installation times and game loads times can be quite a lot faster, gaming itself however will not benefit from this.
Which SSD's to buy?
Early versions of SSD's gave poor performance and some had stuttering write problems, avoid really old SSD's like the plague. Most SSD's manufactured from 2011 onwards should have little to no problems if you update the firmware to the latest version. ADATA ssd's are known for being unreliable, stay clear from these.
NvME vs AHCI:
'Non-Volatile Memory Express' vs 'Advanced Host Controller Interface'. AHCI was created by Intel for SATA mechanical hard drives. The specification describes a system memory structure for computer hardware vendors to exchange data between host system memory and attached storage devices. This was included in windows vista, more info: https://en.wikipedia.org/wiki/Advanced_Host_Controller_Interface
NVM Express, NVMe, or Non-Volatile Memory Host Controller Interface Specification (NVMHCI), is a specification for accessing solid-state drives (SSDs) attached through the PCI Express (PCIe) bus. more info: https://en.wikipedia.org/wiki/NVM_Express
The NVMe device interface has been designed from the ground up, capitalizing on the low latency and parallelism of PCI Express SSDs, and complementing the parallelism of contemporary CPUs, platforms and applications.
The first NvME drive drive released was a Samsung enterprise drive in 2013.
Microsoft added native support for NVMe to Windows 8.1 and Windows Server 2012 R2. Native drivers for Windows 7 and Windows Server 2008 R2 have been added in updates. Linux kernel 3.3 added support for NvME. MacOS 10.10.3 added support for NvME.
What are mSATA, SATA Express, M.2, U.2 and U.3?:
M.2 (formerly known as NGFF a.k.a Next Generation Form Factor). Image of an M.2 SSD:
mSATA is 30mm wide and 50.95mm long, this standard is no longer used. M.2 is 22mm wide and the length is one of the following: 30mm, 42mm, 60mm, 80mm or 110mm.
More info about M.2: https://www.sata-io.org/sata-m2-card
M.2 can either be used with the SATA bus or the PCI-E bus. SATA will limit it to 6Gbps (real world speed of 560MB/s), you can buy M.2 PCI-E drives that offer up to 12,000MB/s real world real speeds as of April 2023. The M.2 specification provides four PCI Express lanes and one SATA 6Gbps port, exposed through the same connector, allowing use of both PCI Express and SATA storage devices in form of M.2 cards. Exposed PCI Express lanes provide a pure PCI Express connection to the storage device, without any additional layers of bus abstraction.
U.2 (formerly known as SFF-8639) More info about U.2: http://www.anandtech.com/show/9363/sff8639-connector-renamed-as-u2
U.3 is a newer enterprise ssd standard.
SATA Express was a newer standard that failed to catch on, instead M.2 caught on.
SSD speeds:
Current 2.5" SATA SSD's max out at approximately 560MB/s sustained read and write speeds. The random read/write speeds for SATA 6Gbps SSD's is a maximum of 100,000 iops read and write. These iops and max read/write speeds are the maximum that the SATA 6Gbps bus can cope with. Iops is the number of input and output operations per second, it is used frequently to compare the real-world speeds of SSD's when transferring lots of small files such as when used as a web server or database server.
Nand vs V-Nand vs 3D-Nand and nanometer processes:
Producing memory below 20nm in size became very difficult as errors are much more common at low nanometer process sizes. As a result you need a good quality controller to be able to detect these errors and allocate portions of the SSD to use instead of the faulty portions detected. Lower nm processes require huge investment and often produce low yields for quite some time until the problems have been fixed. As a result of the errors that occur and the large investment required, memory manufacturers are moving to 3D nand flash memory instead which is usually made in a large well established high yield nanometer processes. This involves stacking the memory circuits on top of each other, chips will use up to 172 layers which will lead to lower cost and and lower power consumption.
Are SSD's good for servers and datacentres and are there different types for those?:
YES! However if you are planning to use an SSD for a business server such as a web server, database server etc then you should buy a datacentre specific SSD which often have 'DC' in the model name. Datacentre SSD's are not the same as consumer SSD's, they are optimised for sustained write speeds rather than maximum speed. One of the reasons is because the processor on the SSD can get quite warm if you were to write data constantly at full speed for several minutes. More info: http://www.anandtech.com/show/9396/samsung-sm951-nvme-256gb-pcie-ssd-review/3 Non-datacentre SSD's used for such purposes can be multiple times slower when used for this purpose so make sure you buy a datacentre-specific SSD (preferably Intel) if you are planning on using an SSD for such purposes.
Over-provisioning:
This is whereby the memory chips on your SSD are larger than the capacity you are able to use. For example you may have an SSD with 512GB worth of nand memory chips but the SSD is sold to you as as 480GB drive. This is because SSD memory sectors can become faulty, as a result the SSD keeps some sectors as spare that it can re-allocate when it notices some faulty sectors. SSD's used to require a very significant amount of over-provisioning in the first few years, but now they usually use less than 10% due to better error checking algorithms.
What is an 'SSHD' a.k.a 'Hybrid SSD'?:
A hybrid SSD was a regular mechanical hard drive with some nand flash memory inside too. These never became popular: https://en.wikipedia.org/wiki/Hybrid_drive http://www.intel.com/content/dam/ww...gy-briefs/smart-response-technology-brief.pdf
Data corruption and retention:
Data corruption can occur if there is a loss of power: http://www.infoworld.com/article/26...risk-massive-data-loss--researchers-warn.html http://www.zdnet.com/article/how-ssd-power-faults-scramble-your-data/
Data can be retained for 1yr or longer without power being connected to an SSD if the room temperature is 30c or lower. If the room temperature is 55c or higher the data may only be retained for 7 days or more. So make sure you keep the psu on your desktop switched on so that a trickle of power is sent to your SSD. If you are using a laptop make sure the power cord is connected or that a battery with some charge is connected and this won't be a problem, more info:http://www.anandtech.com/show/9248/the-truth-about-ssd-data-retention
DRAM-less SSD's:
Manufacturers started making SSD controllers without the need to use LPDDR2 or newer memory several years ago, these require less chips, use less power and are won't lose data in the event of a power failure, LPDDR2 memory is volatile, nand is not. The downside to getting rid of LPDDR2 memory is that the performance is reduced. This is why these controllers will be used only in low-end SSD's in order to reduce cost.
File Systems:
SSD's can be formatted with a variety of file systems such as NTFS, EXT4, BTRFS etc. Samsung has created a new file system specifically designed for flash memory called F2FS (flash-friendly file system). F2FS is open source and patent-free and is available on linux and android. Samsung's own mobile devices already use F2FS with android, so do many Motorola mobile devices. More info: https://en.wikipedia.org/wiki/F2FS
Why are larger capacity SSD's often faster than smaller ones?:
The reason that smaller drives are often slower is that the speed of each individual memory chip is usually not the speed that the drive is rated for. The controller allows the chips to work together to combine the speed of the chips together resulting in faster speed. Smaller capacity drives have fewer memory chips therefore sometimes the combined speed of the chips isn't is fast as with higher capacity drives. This problem has greatly reduced over the past few years as the speed of each individual chip has increased due to the use of 3d-nand flash chips.
Here is a great SSD program to give you information about your ssd:
CrystalDiskInfo: http://crystalmark.info/download/index-e.html
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