SSD(SOLID
STATE DRIVES)
A solid-state drive (SSD) (sometimes referred to as
a "solid-state disk" or "electronic disk") is a data
storage device that uses integrated circuit assemblies as memory to store data
persistently. SSD technology uses electronic interfaces compatible with
traditional block input/output (I/O) hard disk drives. SSDs do not employ any
moving mechanical components, which distinguishes them from traditional
magnetic disks such as hard disk drives (HDDs) or floppy disks, which are
electromechanical devices containing spinning disks and movable read/write
heads. Compared with electromechanical disks, SSDs are typically less
susceptible to physical shock, are usually silent, and have lower access time
and latency. However, while the price of SSDs has continued to decline in 2012,
SSDs are still about 20 times more expensive per unit of storage when compared
to HDDs.
PCI-E, DRAM, and NAND based SSD
SSDs share the I/O interface technology developed
for hard disk drives, thus permitting simple replacement for most applications.
As of 2010, most SSDs use NAND-based flash memory,
which retains data without power. For applications requiring fast access, but
not necessarily data persistence after power loss, SSDs may be constructed from
random-access memory (RAM). Such devices may employ separate power sources,
such
as batteries, to maintain data after power loss.
as batteries, to maintain data after power loss.
DDR SDRAM based SSD. Max 128 GBand 3072 MB/s.
Hybrid drives combine the features of SSDs and HDDs
in the same unit, containing a large hard disk drive and an SSD cache to
improve performance of frequently accessed data. These devices may offer
near-SSD performance for many applications. An example of a fast controller
today is the SandForce SATA 3.0 (6 GB/s)
SSD controller that supports up to 500
MB per second read and write speeds.
Finally, you may be wondering what an SSD looks like
and how easy it is to replace a hard drive with after-market.
If you look at the images below you’ll see the top and underside of a
typical sized 2.5” SSD, the
technology is encased inside either a plastic or metal case and so it looks
like nothing more than a battery.
The form factor of the SSD is actually the same as a
regular hard drive, it comes in a standard 1.8”, 2.5” or 3.5” size that can fit
into the housing and connectors for the same sized hard drives. The connector used for these standard sizes
is SATA; there are smaller SSDs available that use what’s called mini-SATA
(mSATA) and fit into the mini-PCI Express slot of a laptop.
PCI attached IO Accelerator SSD
MEMORY
Flash
memory-based
Most SSD manufacturers use non-volatile NAND flash
memory in the construction of their SSDs because of the lower cost compared
with DRAM and the ability to retain the data without a constant power supply,
ensuring data persistence through sudden power outages. Flash memory SSDs are
slower than DRAM solutions, and some early designs were even slower than HDDs
after continued use. This problem was resolved by controllers that came out in
2009 and later.
Flash memory-based solutions are typically packaged
in standard disk drive form factors (1.8-, 2.5-, and 3.5-inch), or smaller
unique and compact layouts because of the compact memory.
Lower priced drives usually use multi-level cell
(MLC) flash memory, which is slower and less reliable than single-level cell
(SLC) flash memory. This can be mitigated or even reversed by the internal
design structure of the SSD, such as interleaving, changes to writing
algorithms, and higher over-provisioning (more excess capacity) with which the
wear-leveling algorithms can work.
DRAM-based
SSDs based on volatile memory such as DRAM are
characterized by ultrafast data access, generally less than 10 microseconds,
and are used primarily to accelerate applications that would otherwise be held
back by the latency of flash SSDs or traditional HDDs. DRAM-based SSDs usually
incorporate either an internal battery or an external AC/DC adapter and backup
storage systems to ensure data persistence while no power is being supplied to
the drive from external sources. If power is lost, the battery provides power
while all information is copied from random access memory (RAM) to back-up
storage. When the power is restored, the information is copied back to the RAM
from the back-up storage, and the SSD resumes normal operation (similar to the
hibernate function used in modern operating systems).
SSDs of this type are usually fitted with DRAM
modules of the same type used in regular PCs and servers, which can be swapped
out and replaced by larger modules.
A remote, indirect memory-access disk (RIndMA Disk)
uses a secondary computer with a fast network or (direct) Infiniband connection
to act like a RAM-based SSD, but the new faster flash memory based SSDs already
available in 2009 are making this option not as cost effective.
Cache
or buffer
A flash-based SSD typically uses a small amount of
DRAM as a cache, similar to the cache in hard disk drives. A directory of block
placement and wear leveling data is also kept in the cache while the drive is
operating. Data is not permanently stored in the cache. One SSD controller
manufacturer, SandForce, does not use an external DRAM cache on their designs,
but still achieves very high performance. Eliminating the external DRAM enables
a smaller footprint for the other flash memory components in order to build even
smaller SSDs.
Box form factors
Many of the DRAM-based solutions use a box that is often designed to fit in a rack-mount system. The number of DRAM components required to get sufficient capacity to store the data along with the backup power supplies requires a larger space than traditional HDD form factors.[citation needed]
[edit]Bare-board form factors
Form factors which were more common to memory modules are now being used by SSDs to take advantage of their flexibility in laying out the components. Some of these include PCIe, mini PCIe, mini-DIMM, MO-297, and many more.] The SATADIMM from Viking Technology uses an empty DDR3 DIMM slot on the motherboard to provide power to the SSD with a separate SATA connector to provide the data connection back to the computer. The result is an easy-to-install SSD with a capacity equal to drives that typically take a full 2.5 in drive bay. At least one manufacturer, InnoDisk, is producing a drive that sits directly on the SATA connector on the motherboard without any other support or mechanical mount.Some SSDs are based on the PCIe form factor and connect both the data interface and power through the PCIe connector to the host. These drives can use either direct PCIe flash controllers[54] or a PCIe-to-SATA bridge device which then connects to SATA flash controllers.[55]
Good, i recently looking for some infomation about ssd, after reading your post i learned a lot.
ReplyDeleteHi..thanks for giving good information.
ReplyDelete"Om Nanotech offer complete range of memory components from Samsung. We are DRAM Components Supplier Distributor in India Delhi/NCR."