Samsung 840 Pro 256GB SSD Review

Author: AkG
Date: May 14, 2014
Product Name: 840 Pro
Part Number: MZ-7PD256BW
Warranty: 5 Years
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Introducing the Samsung MDX controller

Much like the 840 Pro SSD it is used in, Samsungís MDX controller represents the culmination of decades worth of engineering experience. While there will invariably be a certain amount of comparison drawn between ex-Samsung employee created Indilinx controllers like the Barefoot 3, competitorsí offerings such as the Intel X25 Gen3, and the Samsung MDX, the MDX is rather distinctive.

As a whole, much of that distinctiveness has allowed it to prevail as one of the premier controllers for so long. Its design philosophy results in a radically different approach to several key concepts, one of which is the actual design of the controllerís internal architecture. Much like CPUs which power our systems today, the MDX is a multi-core design but unlike competitorsí similar approaches which use two main processors and sometimes a third low power 'co-processor' for dedicated tasks, the MDX is a true triple core design. Samsung uses three full power ARM Cortex R4 processors, each running at 300Mhz.

Even when compared against newer controllers, this additional fully functional logic blocks gives the MDX a lot more overall power, flexibility and spare clock cycles than most other architectures. Each of these cores can simultaneously handle different tasks as well. For example, one core can allocated for read requests, another for write requests and third can be used to either handle background garbage collection, ensuring the other cores have access to fresh NAND cells. That third core can even double up on either read or write tasks when queue depths call for enhanced low level throughput.

This flexibility can help keep the drive from entering a degraded state or over-saturating one element of the architecture and also explains why the 840 Pro is able to boast such high sustained IO potential. In fact, the MDX was one of the first mass-market controllers that made sustained IOPS performance a priority, even at the expense of sequential performance.

With all of this being said, itís important to remember this controller was released back in 2012, back when most companies were only concerned with pushing the synthetic IOPS boundaries. It is arguable that the MDX itself is the main reason why Intel, Marvell and others have moved towards sustainable performance.

Even though certain controllers such as Intel's X25 Gen3 have surpassed the MDX in the sustained bandwidth department the MDX is still able to compete against most of the competition well past the usual release cycle of a controller.

The MDX is also more power efficient while still being able to handle extremely taxing read and write requests. Thanks to advanced firmware the cores can enter an idle state, allowing for even more power savings. For home users this power saving is negligible but in mobile devices it can have a major impact on battery life.

The last major difference between the Samsung MDX and most other controllers is in durability and longevity department. Like all modern controllers Samsung has implemented advanced ECC to ensure data integrity but theyíve gone the extra mile to put their architecture through much longer testing period, something thatís normally reserved for high end enterprise-class products. In conjunction with heavy NAND screening, this has given Samsung the luxury of boasting one of the lowest drive failure rates in the industry for numerous years.

The MDX also makes use of auto-encryption with AES routines. While 256-bit is considered the de-facto standard these days, it was offered this level of security back in 2012. By default, Samsung has disabled AES encryption but it can be initiated via software on a case by case basis. This added flexibility allows the controller to be more adaptable to the needs of individual clients. Using the built-in AES encryption routines will impart a certain amount of performance loss due to increased processing overhead, but the additional Cortex R4 processor should minimize this impact.

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