Understanding SSD System Requirements
SATA Interface Basics
SATA is the name of the interface standard that allows a storage device, in this case an SSD, to communicate with a host system, in this case a PC or laptop. It facilitates the functioning of all storage features, from basic input/output (or read/write) requests to advanced AHCI-enabled features like Native Command Queuing (NCQ), hot-swapping, power management, and RAID. SATA has gone through several revisions in its lifetime, boasting significant performance gains with each iteration. The SATA interface generation a PC is equipped with will have a direct impact on maximum SSD performance. For this reason, it is crucial to understand the difference between each SATA revision and the capabilities each will afford a modern SSD.
Released in 2003, SATA I, also known as SATA 1.5Gb/s, is the first generation of the SATA specification. As its name implies, it is able to communicate at up to 1.5Gb/s. This early revision does not support some modern storage features, such as Native Command Queuing. Maximum transfer rates are around 150MB/s, slightly better than the older PATA interface (also called UDMA 133) it replaces, which had a maximum speed of 133MB/s.
SATA 2.0, also known as SATA 3Gb/s, is the second generation of the SATA specification. Released in 2004, it is capable of communicating at up to 300MB/s. This revision also introduces Native Command Queuing (NCQ), a feature that improves multitasking performance. SATA 2.0 is more than capable of handling the best hard drives on the market, but it is easily overwhelmed by the onslaught of Flash devices (SSDs) that are now popular. Computers purchased in 2005 or later are likely equipped with SATA 2.0 support.
Released in 2009, SATA 3.0, also known as SATA 6Gb/s, is the third generation of the SATA specification. It is capable of communicating at up to 600MB/s, with overhead taken into account. In addition to its speed improvements, this revision also introduces NCQ management, improved power management features, and queued TRIM support (allowing TRIM commands to be queued with I/O requests, which was not possible on earlier implementations). While it is currently capable of supporting the massive speeds of today’s SSDs, it is already being outpaced as SSD technology advances. This is the standard that most modern SSDs are built to support, although they are backwards compatible with the earlier standards as well.
Building upon the foundations of SATA 3.1, mSATA was designed to address the rising trend of continually shrinking Notebook computers. Smaller profile laptops require smaller SSDs, which in turn require smaller connectors. Notebooks that feature the mSATA interface are becoming more popular but still represent a relatively small portion of the overall market. Maximum transfer speeds are equivalent to the standard SATA 3.0 interface.
SATA Express, once finalized in 2013, will be capable of speeds faster than SATA 6Gb/s thanks to its use of the PCI Express (PCIe) interface. Interface speeds may be increased to 8Gb/s or 16Gb/s (or perhaps even higher speeds later). Future motherboards will offer slots for both SATA Express and traditional SATA devices, and the SATA Express interface will be backward compatible with the standard SATA 3.0 interface.
How SATA Affects SSD Performance
Most SSDs available on the market today are designed for SATA 6Gb/s (SATA 3.x). Many consumers still have older machines, however, which do not have support for the latest SATA revision. Fortunately, SSDs are backwards compatible with older SATA versions. They will, however, be limited by the maximum bandwidth supported by the host machine (e.g. a SATA 6Gb/s SSD connected to a SATA 3Gb/s computer will not be able to reach transfer speeds more than 300MB/s, even though the drive might be rated for performance well over 500MB/s). This is why it is important to understand the capabilities of existing PC hardware before upgrading to an SSD – to avoid any potential disappointment if speeds do not match advertised rates.
Samsung knows that many people still use older computers with SATA 2.0 at home or work, and these people can still greatly benefit from an SSD upgrade. During its design process, Samsung optimized the 840 Series SSD for maximum performance on all SATA interfaces, current and legacy. An 840 Series SSD will outperform both an 830 Series (SATA 6Gb/s) and a 470 Series (SATA 3Gb/s) SSD connected to the same SATA 3Gb/s port, as shown in the table below.
In fact, an 840 Series SSD will outperform any SATA 3Gb/s SSD on the market on the same system setup. An investment in an 840 Series SSD is, therefore, future-proof in that an upgrade now will benefit a SATA 3Gb/s system, but the SSD will also be ready to offer even better performance in the event that one decides to upgrade to a SATA 6Gb/s system in the future. Drives designed specifically for an older SATA revision are limited by their aging hardware and will be unable to saturate the available bandwidth on any SATA interface.
Speaking of computer upgrades, SATA expansion cards are widely available in the market. These cards promise to add and/or upgrade SATA ports on an existing system. They are limited, however, by a certain amount of overhead and will often not be capable of providing a modern SSD with the throughput it needs to reach maximum performance. Thus, Samsung recommends connecting your 840 Series SSD to a native SATA 3.0 (6Gb/s) port to enjoy its full potential.
Locating a native SATA 3.0 (6Gbp/s) port is relatively simple, but it requires some attention to detail. Most motherboards include both SATA 3.0 and SATA 2.0 ports, and they are often located side-by-side. While they are usually color-coded, there is no industry standard defining which color represents which SATA revision. Hence, it is important to carefully read the labeling to determine which is which.
Maximize SATA Capabilities with AHCI
AHCI, Advanced Host Controller Interface, is an open interface championed by Intel to allow the use of advanced SATA features (e.g. NCQ, hot plugging, power management). Basically, it defines a standard method for storage devices from various vendors to communicate with the host system, allowing software engineers to take advantage of specialized functionality. In order to enjoy the full performance of your Samsung 840 or 840 PRO Series SSD, AHCI mode must be enabled on your system through the BIOS.
If AHCI is not properly configured on your system, the Random Read/Write performance of your SSD will be limited to a Queue Depth of 1 (QD1), severely limiting the performance improvements you will notice over a conventional Hard Disk Drive (HDD) while multi-tasking (by 80-90%). Since the latest versions of Windows, including Windows Vista and Windows 7, include standard AHCI drivers, there is no need to install AHCI drivers manually. Some older systems, however, may not support AHCI even if they are equipped with a SATA 3 (6Gb/s) interface. Samsung’s Magician software can help you determine whether or not AHCI is supported and/or enabled on your PC.
How do I enable AHCI?
Most modern PC systems support AHCI mode and enable it by default. If it is not enabled on your system for some reason, however, you can manually enable it via your computer’s BIOS. The procedure will vary slightly depending on the BIOS version on each system, but the general steps are the same: Restart the computer and press the appropriate key to enter the BIOS (this is usually DELETE, F2, or F10); Find the section for “Integrated Peripherals” or “Storage configuration;” Change “Configure SATA as” or “PCH SATA Control Mode” to “AHCI.” Consult your PC’s user manual for instructions for your specific machine.
Ideally, AHCI mode should be enabled via the BIOS BEFORE installing the Operating System (OS). On newer systems, this is generally the case. If it is not, and AHCI is enabled via the BIOS for a Windows Installation that was not originally configured for AHCI, it is not uncommon for stability problems to arise. Windows XP does not include native AHCI drivers, making it more complicated to enable AHCI mode because it is the user’s responsibility to locate and install the correct AHCI drivers for the OS. In general, PC chipset vendors (e.g. Intel, AMD, nVIDIA) maintain their own AHCI drivers for Windows XP users. It is best to consult the website of your motherboard vendor or PC manufacturer to be sure.
What specific advantages does AHCI provide to Samsung SSDs?
Significantly Lower Power Consumption
AHCI mode is required for Samsung’s SSDs to demonstrate their superior power consumption. This is because, without AHCI, the SSD cannot communicate with the host system to take advantage of advanced power management features like Host-Initiated Power Management (HIPM) and Device-Initiated Power Management (DIPM). Maintaining the physical SATA interface (called the PHY) consumes a considerable amount of power, and HIPM and DIPM allow for the PHY to be put into a reduced power mode. After some predetermined period of inactivity, either the host or the device can signal the PHY to enter its reduced power state. Samsung’s 840 and 840 Pro Series SSDs make aggressive use of DIPM to put the PHY into reduced power consumption mode, contributing to the drive’s reputation for having the industry’s lowest idle power consumption.
Without HIPM or DIPM, power consumption will increase dramatically, as shown in the graph below via drive “C,” which does not use these power management features. In general, such power management features are enabled by default on laptop systems. Desktops, which are free from battery constraints, generally operate with these features disabled – thus increasing drive power consumption in favor of slight performance advantages.
AHCI also affects the ability of Samsung’s SSDs to reach their maximum Random QD32 performance. This is because AHCI is required for Native Command Queuing (NCQ) to function. Because SSDs enjoy extremely fast speeds, storage is no longer the bottleneck of a PC system. NCQ helps an SSD deal with situations where it finds latency on the host, a phenomenon unheard of with traditional HDDs. Additionally, NCQ allows the SSD controller to process commands in parallel, improving performance and reducing latency.
AHCI is also required in order to enable “hot plugging,” a kind of plug-and-play functionality that allows an SSD to be plugged into or removed from a system without the need to shut the computer down. This is convenient for multi-drive systems where an SSD is in use as a secondary drive. Rather than having to quit all running programs and shut down the computer, a new secondary SSD can be inserted to complement or replace an existing drive without adding unnecessary steps to the workflow.
What if my system doesn’t support AHCI?
If you have a system that does not support AHCI, or if you fail to enable it properly, your system will run in “IDE emulation” mode, a kind of compatibility mode that mimics the functionality of the older “Integrated Drive Electronics” ATA interface. While your SSD will not display its full performance potential or be able to take advantage of all of the latest SATA functionality, it will still be able to function on your system.
Enabling AHCI is crucial to get the most performance out of your Samsung SSD. If you notice that performance is lower than expected, one of the first things to check is whether or not AHCI is properly configured. Samsung’s latest Magician 4.0 software can assist in determining if AHCI is supported and/or enabled. Once set up, AHCI will enable your Samsung SSD to achieve superior performance, lower power consumption, and improved convenience.
Enhancing SATA Performance with RAID
Today’s SSDs are maximizing the performance potential of the current SATA 3.0 interface generation. One way to increase performance beyond standard single drive SATA configurations is to pair 2 or more drives together using SATA’s native RAID support.
RAID, which stands for Redundant Array of Independent/Inexpensive Disks, is a type of storage system in which a number of drives (at least 2) are combined into one logical unit. RAID is used to improve performance, improve reliability, or some combination of these two. Data can be distributed among the drives in a RAID array in one of several ways (called RAID levels). The most common RAID levels are RAID 0 and RAID 1. With the introduction of its 7 Series Chipsets and the latest Intel Rapid Storage Technology (IRST) drivers (11.0 or later), Intel is now fully supporting SSD technology, including the TRIM maintenance command, in RAID 0 arrays. In the past, the lack of TRIM for RAID 0 was a source of frustration, as the performance improvements initially gained through the RAID array were mitigated by the performance deficits caused by the lack of TRIM. Thus, with the addition of TRIM support for RAID 0, it is useful to understand RAID technology and who (and why) an individual might choose to use it.
RAID 0, which requires a minimum of two drives and whose primary purpose is speed, divides files into chunks, or stripes, which are split among the available drives and written in parallel. By doing this, it is also possible to read smaller sections of the original file in parallel. This parallelism is what allows for the drastic performance improvements that RAID 0 offers. If one drive fails, however, all data (having been broken into chunks) is destroyed; and the likelihood of failure increases as more drives are added to the array.
RAID 1, which also requires a minimum of two drives, writes data identically to multiple drives and offers performance similar to a single SSD. Its purpose is redundancy. As such, the array will continue to operate as long as at least one drive is still functioning. Capacity is limited to the size of the smallest drive in the array. The primary goal is to reduce downtime in the event of a hardware failure. However, this solution, despite its redundancy, is not a replacement for a good backup regimen, as it cannot protect from data corruption or security breaches.
Who should use RAID?
Any desktop user can implement RAID on their system with relative ease, but only a certain subset of users will be able to truly justify the expense and benefit from what it has to offer. As outlined above, each implementation has a different purpose.
RAID 0, thanks to its incredibly fast read and write speeds, is ideal for an individual who must work with large files that need to be modified or written quickly, such as a graphic designer who spends a lot of time in Adobe Photoshop or a videographer who uses Avid to edit digital video files. Some gamers also enjoy the performance advantages that RAID 0 provides. Because it lacks redundancy, however, RAID 0 is not suited for mission-critical tasks and should be supplemented by a robust backup system.
RAID 1, which writes all data identically to two or more drives, is ideal for mission-critical workloads, such as small servers, that cannot experience significant downtime. The speed is the same as it would be with a single disk, so there is no performance advantage or disadvantage. The sole benefit is its redundancy, which will make it easier to get up and running in the event that one SSD fails. As mentioned above, RAID 1, despite its redundancy, is not an alternative to a solid backup. It cannot protect against user error (e.g. inadvertently deleting files) or data corruption.
Samsung, as the largest supplier of SSDs to the preinstalled market, must qualify its SSDs on an endless variety of hardware configurations, including all current and legacy SATA interfaces. Its SSDs are designed to outperform the competition on all SATA implementations, making a Samsung SSD the smartest choice for any PC upgrade, regardless of whether it is an aging or a state-of-the-art system.