Solid State Disk or Solid State Drive, also known as electronic hard disk or solid state electronic disk, is a hard disk consisting of a control unit and a solid state storage unit (DRAM or FLASH chip). Because solid state drives do not have the rotating media of a regular hard disk, they are extremely resistant to shock and vibration.
Flash-based SSD (IDE FLASH DISK, Serial ATA Flash Disk): Using FLASH chips as the storage medium, this is what we usually call an SSD, which can be made in a variety of ways, such as laptop hard drives, microdisks, memory cards, flash drives, and other styles. The biggest advantage of this kind of SSD solid state drive is that it can be moved and the data protection is not controlled by the power supply, it can be adapted to a variety of environments, but the service life is not high, which is suitable for individual users. In flash-based SSDs, the storage cells are divided into two categories: SLC (Single Layer Cell) and MLC (Multi-Level Cell).SLC is characterized by high cost, small capacity, but fast speed, while MLC is characterized by high capacity and low cost, but slow.MLC is 2bit per cell, which is a whole lot more than SLC. MLC is 2 bits per cell, which is exactly twice as much as SLC. However, due to the more information stored in each MLC storage unit, the structure is relatively complex, the chances of error will increase,hollister france, must be error correction, this action leads to its performance is significantly behind the simple structure of the SLC flash memory. In addition, the advantage of SLC flash memory is that the number of rewrites is up to 100,000 times, 10 times higher than MLC flash memory. In addition, in order to ensure the life of MLC, the control chip are checksum and intelligent wear and tear balance technology algorithms, Cixi hard disk data recovery, so that the number of writes per storage unit can be shared evenly, to 1 million hours between failures (MTBF).
DRAM-based SSD
DRAM-based SSD: DRAM is used as the storage medium and is currently used in a narrower range of applications. It mimics the design of a traditional hard drive, can be configured and managed by the file system utility of most operating systems, and provides industry-standard PCI and FC interfaces for connecting to host computers or servers. Applications can be categorized into SSD drives and SSD drive arrays. It is a high-performance memory and has a long lifespan. The downside is that it requires a separate power supply to protect data security.
Advantages of SSDs
Solid State Drives have the following advantages over regular hard drives:
Fast startup
No motor to accelerate the spinning process.
Small read latency
No magnetic heads, fast random reads with minimal read latency. According to the relevant tests: two computers in the same configuration of the computer, equipped with solid state hard disk notebook from boot to appear desktop a *** only 18 seconds, while equipped with a traditional hard disk notebook total *** with 31 seconds, the two almost have almost half the difference.
Fragmentation doesn't affect read times
Relatively fixed read times. Since addressing time is independent of where the data is stored, disk fragmentation does not affect read times.
Fast write speeds
DRAM-based SSDs are extremely fast to write to.
No noise
Because there are no mechanical motors or fans, the noise level during operation is 0 dB. Some high-end or high-capacity products are fitted with a fan, so noise will still be generated.
Lower heat generation
Low-capacity flash-based SSDs consume less power and generate less heat during operation, but high-end or high-capacity products will consume more.
No mechanical failure
There are no mechanical moving parts inside, so no mechanical failure will occur, and there is no fear of collision, shock, or vibration. This does not affect normal use even when moving at high speeds or even when tilted over, and minimizes the possibility of data loss when the laptop is accidentally dropped or collided with a hard object.
Larger operating temperature range
Typical hard drives only operate in the 5 to 55 degree Celsius range. Most SSDs can operate in temperatures from -10 to 70 degrees Celsius, and some industrial-grade SSDs can operate in temperatures from -40 to 85 degrees Celsius and beyond (e.g. -55 to 135 degrees Celsius for RunCore military-grade products).
Smaller and lighter
Lower-capacity SSDs are smaller and lighter than drives of the same capacity. However, this advantage diminishes as capacity increases. Up to 256GB, SSDs are still lighter than regular hard drives of the same capacity.
Disadvantages of SSDs
Solid-state drives have the following disadvantages when compared to traditional hard drives:
High cost
Price per unit of capacity is 5 to 10 times higher than traditional hard drives (based on flash memory) or even 200 to 300 times higher (based on DRAM).
Low capacity
The maximum capacity of SSDs is currently much lower than that of traditional hard disks. The capacity of traditional hard disks is still growing rapidly, and IBM has reportedly tested a 4TB traditional hard disk.
Susceptibility to external influences
Because they are not shielded in a Faraday cage like traditional hard disks, SSDs are more susceptible to the adverse effects of certain external factors. For example, power outages (especially in DRAM-based SSDs), magnetic field interference, static electricity, and so on.
Limited write life
Limited write life (flash-based). Typical flash memory has a write life of 10,000 to 100,000 cycles, and specialized ones can have a write life of 1,000,000 to 5,000,000 cycles, yet some parts of the file system (such as the file allocation table) will still be written to more than this limit throughout the life of the computer. A purpose-built file system or firmware can share the write locations, giving the SSD an overall lifespan of 20 years or more.
Data is difficult to recover
Data is difficult to recover from corruption. Once the damage occurs in the hardware, if it's a traditional disk or tape storage method, you may still be able to salvage some of the data through data recovery. But with solid state storage, once the chip is damaged, it's almost impossible to recover data from a chip that's been broken into several pieces or pierced by an electrical current. Of course, this shortcoming can be sacrificed to make up for the storage space, mainly with RAID 1 to realize the backup, and the traditional storage backup principle is the same. Because of the current high cost of SSDs, it is still expensive to backup in this way.
Shorter battery range
Based on real-world testing, laptops using SSDs have shorter battery ranges than 2.5-inch traditional hard drives using 5400RPM in idle or low-load operation.
Higher power consumption
DRAM-based SSDs consume more power than traditional hard drives at all times, especially when they are turned off and still require power or data loss.
Frequent false positives on Windows XP
Users have reported that MLC-based SSDs can cause false positives on Windows XP. This is due to the fact that the file system mechanism of Windows XP is not suitable for SSDs. Windows 7 is optimized for SSDs and disables traditional hard drive mechanisms such as SuperFetch, ReadyBoost, and startup and program prefetching, allowing for better SSD performance.
Solid-state drive vs. traditional hard drive advantages and disadvantages
Items
Solid-state drives
Traditional hard drives
Capacity
Smaller
Larger
Price
Higher
Lower
Random access
Extremely fast
Average
Writes
SLC: 100,000
MLC: 10,000
Unlimited
In-disk arrays
May be
Extremely difficult
Operating noise
No
Yes
Operating temperature
Extremely low
More noticeable
Shock protection
Very good
Worse
Data recovery
Difficult
Can be done
Weight
Light
Heavy
[3]
The table above is a comparison between the characteristics of SSDs and traditional hard drives. As you can see, SSDs have the following advantages over traditional mechanical hard drives:
1. Access speed: SSDs use flash memory as the storage medium, and the read speed is faster than mechanical hard drives, and the seek time is almost zero, so that when used as a system disk, it can significantly accelerate the operating system startup speed and software startup speed.
2. Anti-vibration performance: SSDs have no mechanical structure at all, so they are not afraid of vibration and shock, and do not have to worry about unavoidable data loss due to vibration.
3. Heat and power consumption: SSD solid state drive is different from the traditional hard disk, solid state drive, there is no disc high-speed rotation, so the heat is significantly lower than the mechanical hard disk, and the FLASH chip power consumption is extremely low, which means that the battery life of the notebook users to increase.
4. Noise: SSDs do not have a platter mechanism, so there is no head arm tracking sound or high-speed rotation noise, so there is no noise at all when the SSD is working.
However, although the performance of SSDs is very attractive, there are many advantages, but the price, capacity, and the limited number of times the data can be read and erased, and other shortcomings should not be underestimated:
1. Write speed: Write speed is the bottleneck of the majority of SSDs, especially for the small file write speed is still far from adequate, which is related to the characteristics of the flash memory chip itself.
2.
2. Lifespan issues: Flash chips have a lifespan, and their average lifespan is much lower than that of a mechanical hard drive, which puts SSDs at risk as a storage medium.
3. Cost-effective problem: At present, the price of SSDs is still relatively expensive, and the price per G unit is tens of times higher than that of traditional hard disks, which is not affordable to the average consumer.
Solid state hard disk products
Existing solid state hard disk products have 3.5 inches, 2.5 inches, 1.8 inches and other types of capacity is generally 160GB ~ 1TB, much larger than the average flash drive (U disk). The interface specifications are the same as those of traditional hard disks, with UATA, SATA, SCSI, and so on.
For example, RunCore's product line covers all the standard interfaces for SSDs, including the mini-PCIe interface for netbooks, the Zif interface, and the 1.8" Lif interface designed specifically for the Mac air.
At CES 2008, professional SSD maker BitMicro Networks showed off the internals of a professional-grade SSD with a SCSI interface (see right). The product has 32 TSOP-packaged NAND flash chips soldered to a single PCB, and BitMicro revealed that the product averages about $10 per gigabyte, about five times the price of a mainstream mechanical hard drive.
Lanco also launched what it claimed was the country's first solid-state drive product in 2008. And Yizheng claimed to have launched the country's first solid-state drive in 2007. The company also launched the world's fastest SSDs, followed by Magnesium, which claimed to have launched a SSD with a speed of 1GB/S (using SSDs as arrays).
Solid-state drive security
Solid-state disk drives may offer better data security than traditional hard disk drives, but experts say it doesn't completely erase data and is less resistant to physical attacks from Light Sources' high-output-type lamps such as ultraviolet lasers.
Despite their relatively high cost and better durability, solid-state disk drives are popular, especially in portable computers, because they feature low power consumption and fast data access. Experts say securing data on solid-state disk drives will become more of a concern as the technology becomes more widely used and penetrates other handheld devices such as smartphones.
Many solid-state disk drives use industry-standard NAND flash chips designed for camcorders and MP3 players, so they don't have physical security vulnerabilities that would prevent them from being moved from their storage containers, said Jim Handy, president of Objective Analysis, a semiconductor research and consulting firm. A hacker can easily detach the NAND chip from the solid-state disk drive and then use a flash chip program to read the data on it. Once the data has been read, data recovery software can be used to reorganize the files. there's really nothing complicated about the process, Handy said. Bunnie, a hacker who specializes in attacking chips at the blog site bunnie studios, said another physical attack involves the use of an ultraviolet laser to remove the lockbit, or cryptolocker ---- which sits on the chip's fuse and is used to protect the solid-state disk drive. After the lockbit is removed, the data array on the SSD can be read using standard methods, Bunnie said: Once the data is unlocked, no special equipment is needed at all to be able to read the data array. For example, the data array can be read using a conventional ROM reader, a device that usually means burning and verifying insecure ROM devices. Kilopass Marketing Director Craig Rawlings said that in order to reduce the likelihood of a hacker stealing the data, encryption locks can be integrated into the internal of the SSD drive controller device for solving disk encryption problems from the hardware layer, Kilopass said. Kilopass sells products that use Super Permanent Programmable Memory (XPM) technology to store encryption locks on system-on-chip devices.
While encryption locks can be attacked, experts say that encryption is the number one thing that can be done to secure data on solid-state disk drives. Many companies, including Safend and Encryptx, have products in this area that encrypt data on storage devices such as SSDs.Sean Barry, senior engineer of data recovery at Kroll Ontrack, said encryption adds yet another line of defense, so hackers have to bypass the encryption layer and the controller, and then reorganize the raw data so they can successfully steal the data. This takes a certain amount of time, during which time the data is likely to be invalid or worthless. Encryption also makes it easier to erase files on solid-state disk drives. iFixlt's CEO, Kyle Wiens, says that, like hard disk drives, while SSDs create multiple backups of files, encryption software can help you erase protected files. iFixlt's CEO, Kyle Wiens, says: "Every time you write data to an SSD, chances are that it's written to another part of the drive, which then modifies the directory table. catalog table. In this way, it forgets the address where the data was previously stored. The user may delete a file, but a copy on another partition may still be unharmed.Wiens says that the wear-leveling feature of SSD drives (based on a certain algorithm) equalizes the erasure and writing of data across all the storage chip units, which equalizes the aging rate of each storage chip unit, so that the file is harder to erase completely.Intel Fellow- -- Knut Grimsrud said that some encryption software monitors the loss-balancing process to keep track of file traces, which can then be removed using the Secure Erase command. Secure erase is a command used to securely delete a file and requires support from the encryption software, Grimsrud said: If all the software is writing data at the top level of Logical Block Addressing (LBA), I think it may not be very efficient on solid state disk drives because it may have lost the efficiency gains that were made by the previous loss balancing or other similar features, and the software doesn't know that. and the software doesn't know that. Logical block addressing (LBA) specifies the address where data blocks are stored on a storage device.
In short, it's easier to erase data on a solid-state disk drive than it is on a hard disk drive, which has its ups and downs, said KrollOntrack's Barry, adding that the data is stored on the tubes of the solid-state disk drive, and by eliminating the tubes, the data is flushed out. On hard disk drives, on the other hand, the data has to be overwritten or suffer physical damage to prevent it from being read. barry said data flushing has its own advantages from a fast standpoint, but from a bad standpoint, data on solid-state disk drives tends to be more haphazard and can be easily lost.
Limitations of SSD solid-state storage
While SSD seems vastly superior to disk technology, there are some drawbacks. First of all it is expensive as memory costs almost 100 times more than disk storage. Secondly, they are partly made up of volatile DRAM and once power is lost, the data is permanently lost. To avoid data loss, those SSDs should be protected by a battery backup. Finally, because SSDs are not caches, instead of flushing small blocks of data to non-volatile storage, they copy the entire contents of the SSD. While the capacity and transfer rate for sustained writes varies for the target disk drive or subsystem, a reasonable estimate for this operation is 30-40MB/S.
One way to manage this is to use the disk drive to mirror the SSD, yet there is additional overhead to handle the I/O from the mirrored drive, which negatively affects the overall I/O transfer rate of the S S D. But in any case, at least the time it takes to complete a mirror write operation to a mirrored disk is minimal.
For some reason, including chip density, thermal performance, and so on, SSDs will always have a smaller capacity than disk drives. When disk subsystems are considered, the capacity difference is even more dramatic. This means that applications using SSDs are limited by the storage capacity of the SSD. However, it is worth pointing out that SSDs can be used in disk subsystems to provide high performance storage.
In summary, higher selling prices have hindered the popularity of SSDs, which are several or even dozens of times more expensive than mechanical hard drives of the same capacity.
The current SSD capacity is small, and the current 512GB or even TB hard disk, while the maximum capacity of the SSD SSD is only 512GB, and the price is very expensive. The lack of end device support is also another major problem facing SSDs.
While SSDs are still subject to cost and capacity constraints, with the popularity of the Windows 7 operating system, SSD specifications will continue to be upgraded and the development speed will be further accelerated, and SSDs will still be available tomorrow.
Windows 7 is optimized for SSD technology
While there are still many drawbacks to SSDs, with the continuous improvement in SSD technology development, and the launch of the latest version of Microsoft's Windows operating system, Windows 7, which is more optimized for SSDs, some of the drawbacks of SSDs have been solved.
Windows 7 has better technology for SSD performance and longevity. Without any user intervention, the system automatically recognizes when a storage device is a mechanical hard drive or a solid state drive, and if it is a solid state drive, it turns off the Disk Organizer function to prevent the solid state drive from constantly performing repetitive read and write tasks, thus reducing the wear and tear on the solid state drive's chips. The Trim command effectively prevents SSDs from slipping in speed after a long period of time and extends the life of the flash memory.
Windows 7, by default, automatically detects SSD devices and disables automatic disk disassembly in scheduled tasks, which greatly reduces the wear and tear on SSDs during daily use and increases their lifespan. It is important to know that with current SSD products, the write life of mainstream MLC chip SSDs is only 10,000 times, while expensive SLC chip SSDs are only 100,000 times.
When will SSDs become commonplace?
There is no doubt that SSDs are the pioneers of the next generation of storage media. As people demand more and more speed and stability, the upside of SSDs will continue to be very high. However, although the performance advantages of solid state drives in the future growth potential can not be underestimated, and at present the speed of solid state drives to market seems to be much faster than expected, but the distance from the universal popularity, completely replace the traditional mechanical hard disk is obviously still a considerable distance.
Domestic solid state drive R & D companies
1. Hunan Yuanke High-tech Limited
Research and development personnel mainly from the National Defense University and social recruitment of employees. Mainly for the military, industry, consumer field.
Provide customized or unique function SSD, independent intellectual property rights.
2. Recall Storage Technology (Shenzhen) Co.
Sample in 2007.
3. Wuhan Goodyear Data Technology Co.
Sample in 2008.
4. Huasai
Sample in 2008.
5. Huaheng Weiye (SUNDOM) Technology Co.
Launched for the military industrial enterprises, and server applications, with data "a key to destroy" SSDs, capacity of up to 1TB, read and write speeds of more than 250MB
6. enterprise. The price-performance ratio is relatively high