how to buy an ssd hard drive best buy ssd drive

The hard drive is certainly the component that has evolved the least in our computers while it is the slowest!

The reason for this very slight development is simple:
the hard drive always uses moving parts subject to purely mechanical requirements ??

Since their relative democratization in 2009, the SSDs have not stopped progressing. If their technology remains significantly more expensive than that of mechanical hard drives, the performance of "flash drives" soared once again with the arrival of SATA 6 Gbps in 2010.
Latest generation SSDs now reach transfer rates of over 500 MB / s with an access time of 0.1 ms while the best hard drives are not yet able to support 100 MB / s and that ten ms are necessary to position the read / write heads.
Suffice to say right away, the time to launch applications no longer compares! However, one should not lose sight of certain disadvantages of SSDs, in particular their wear, but in this area, significant progress has been made

The hard drive

The hard drive has established itself as the most common storage system. Over the years, it has evolved but the operating principle remains unchanged. Rotating trays are covered with ferromagnetic material and read / write heads mounted on an arm move between the center and the periphery. The rotational movement of the trays combined with the movement of the heads allows access to the entire disc.
In addition to this mechanical part, the hard disk has an electronic circuit to drive the heads and communicate with the rest of the PC. It also has a cache memory which stores the last data read.
The best hard drives for desktop computers like the Western Digital Velociraptor 300 GB reach an average transfer rate of more than 110 MB / s in read and write with an access time of around 7 ms thanks to their turntables at 10,000 rpm. Due to the large increase in their capacity and therefore the information stored per cm², slower disks also exceed 100 MB / s but with an access time of 12 to 15 ms. Even the recent 2 ½ inch 5400 rpm laptop models for laptops exceed 80 MB / s with a longer access time (18 to 20 ms)

While performance is still improving, gains have become very small over the generations.
Nowadays, hard drives are mainly intended for mass storage with a very low price per GB.

 
Western Digital Velociraptor 300 GB and Seagate Momentus 7200.3 320 GB

A hybrid hard drive?

Seagate is the only manufacturer to offer a “hybrid” hard drive in 2 ½ inch format combining a 4 GB of flash memory with conventional storage on trays. The on-board electronics analyze the files used most often and place them in the flash memory. The start-up of the operating system and current applications is thus significantly boosted. But if the information is not in flash memory, the Momentus XTbehaves like a classic 2 ½ inch 7200 rpm hard drive with 32 MB of cache. The approval of such a disc is proven even if it is still far from offering the comfort linked to the reactivity of a real SSD. The 4 GB of flash memory however induce a significant additional cost. The Momentus XT 500 Go is worth 40 to 50 ?? more than a 7200 rpm 500 GB hard drive, almost double the price. Anyway, this hard drive is an elegant and efficient solution particularly well suited to laptops.

SSD cuvee 2011!

The SSD consists of a memory controller, sometimes assisted by a cache, and NAND chips. In the absence of any mechanical parts, SSDs have an access time of the order of 0.1 ms (compared to 7 ms for the best hard drives). The better performing SLC memory but much more expensive than the MLC has been almost abandoned.
All current mainstream SSDs therefore rely on NAND memory of the MLC type, the main defect of which is to wear out over the cycles of read, write and erase. This problem of cell degradation is now very well managed by the TRIM command integrated into all SSDs and the reservation of several GB to remedy the failure of a few memory cells over time. The arrival of NAND chips in 25 nm cheaper to produce, less energy-consuming but in return more prone to wear than the old engraved in 34 nm revived the controversy on the wear of SSDs. Manufacturers therefore reserve a larger amount of memory in order to work around the problem. The best therefore remains the enemy of good!

Since SSDs use MLC memory, the controller makes all the difference in performance. Intel, Indilinx, SandForce and Marvell offer controllers of very good quality with each their advantages but also disadvantages. For an SSD to offer the best possible performance, it must support the SATA 6 Gbps interface in order to output more than 280 MB / s. But that's not all! To remain more responsive in multitasking, the SSD controller must support a maximum of IOPS (Input / Output Operations Per Second, input / output operations per second).

The ideal SSD should therefore have a SATA 6 Gbps controller capable of transferring more than 450 MB / s, manage more than 25,000 IOPS in read and write and use cells in 34 nm in order to have the greatest possible endurance. The Intel SSD 320 and SSD 510, the Crucial M4 and the Vertex 3 were the most anticipated SSDs at the start of the year. Unfortunately, none of them have all of these qualities. Either the transfer rate is “modest”, or the IOPS are limited, or the cells are at 25 nm… It will therefore be necessary to make a compromise!

The following table illustrates our remarks:

The SSD is however not perfect. In fact, the memory cells used wear out each time they are read or written.
And if an area is used more often, it wears out faster than the others!
The NAND type memory used for SSDs is much less suitable than NOR memory ??
In addition, in the two existing types of NAND, the MLC is the most used while it is the least efficient.
But it is also the cheapest!
By examining the price of SSDs, we quickly understand that the main defect is the price of MB despite the use of the least expensive components.

From a technological point of view, in the SLC memory, the cells are addressed one by one whereas in the MLC, the cells are stacked and addressed in blocks.
In practice, access to a cell is faster, which gives the advantage in terms of SLC performance.
With the MCL, the whole block must be addressed to access a cell and the whole cell block wears out.

OCZ Vertex 3 as well as all SSDs based on SandForce SF-2000 controllers are among the best choices even associated with 25 nm NAND memories (DuraWrite technology reducing wear). They are excellent in IOPS and support SATA 6 Gbps with very high transfer rates.

The Crucial M4 offer very good transfer rates but the IOPS are down compared to the C300 generation which already supported SATA 6 Gbps. In addition, the M4 use 25 nm chips. We expected better to succeed the excellent C300.

Intel SSD 510s offer large capacities with 34nm chips and manage SATA 6 Gbps. Transfer rates are excellent but IOPS very limited. The SSD 510 are especially interesting for their capacities.

Intel SSD 320s use the previous generation controller. They are therefore limited to SATA 3 Gbps, which leads to speed. The IOPS are correct but it is difficult to recommend them in the face of competition.

SSD and HDD always complementary!

Even if hard drives still evolve a little in terms of performance, they are especially interesting for pure storage where their price per GB is particularly low. As an indication, a 2 TB 5400 rpm disc costs around 70 € (a little more than 100 € at 7200 rpm). In a desktop computer, the ideal solution is the combination of a very powerful SSD but of medium capacity (64 or 128 GB for respectively 100 € or 200 €) seconded by a hard disk of high capacity.

In laptops, pending the generalization of solutions comparable to Intel SSD 310 (a mini mSATA SSD leaving the 2 ½ inch bay free for a hard drive), you will have to deal with either a medium capacity SSD (64 or 128 GB ), or invest in a 256 GB SSD still very expensive (more than 400 €). The Momentus XT 320 or 500 GB (100 €) are therefore an interesting alternative.

In terms of SSDs, the 2011 vintage is a little disconcerting insofar as no model is "absolutely perfect". Models based on the SandForce SF-2000 controller like the Vertex 3 have our favors as well as the Crucial M4. The Intel SSD 510 especially are interesting for their high storage capacities but the IOPS are at half mast. As for the SSD 320s, they are hardly recommendable ... Among the older models, the Crucial C300 and the OCZ Vertex 2 (as well as all the SSDs based on the SandForce SF-1200) remain good choices; the arrival of their successors having lowered their prices