Those who have been operating computers for more than 20 years can easily recall the hassle of using the big and wide cable to access the storage drive.
Then, in some time, Serial Advanced Technology Attachment (SATA) Solid State Drive (SSD) replaced this cable due to more speed as well as convenient features for the users.
Implementing an SSD is a reliable way to increase the server or computer speed. Despite the higher cost of SSDs than the Hard Disk Drives (HDDs), they are in high demand.
It is great to implement an SSD for accelerating data access. However, it is essential, although challenging, to select the right drive.
It is worth noticing that no two Flash drives are the same. First, the enterprise-class arrays for use in data centers’ servers and SSDs suitable for notebook computers are different.
The latter usually do not have the same mean time between failure score. Thus, this is one deciding factor to consider.
Next, the specific storage device inside the device helps in deciding the right interface. Usually, the intended SSD interface should match with the one used in the server’s or storage controller’s backplane.
The market is full of different types of SSDs, including the ones relying on SATA and Peripheral Component Interconnect Express PCIe interfaces.
Well, to decide which of the two is most suitable for your projects, it is worth weighing their own pros and cons.
Those who have built PCs or added a hard drive are already aware of SATA connectors. SATA is the present bus interface for joining an SSD, HDD, or an optical drive to the computer. It has replaced the Parallel Advanced Technology Attachment (PATA), as it comes with more visible benefits.
For communication, a SATA controller requires a mode set. The conventional modes are as follows:
- Integrated Development Environment (IDE): Is a slower mode for storage devices and runs as a PATA or IDE drive.
- Advanced Host Controller Interface (AHCI): Is a structure for exchanging data between storage devices and host system memory. It provides a standard method for identifying, setting up, and programming AHCI adapters. It supports Native Command Queuing (NCQ) with hot swapping via a host controller of SATA. SSDs work so fast that it can wait for more work in a given time slot. NCQ facilitates the controller to make a maximum of 32 requests simultaneously.
- Redundant Array of Independent Disks (RAIDs): Allows a computer to use multiple disks as a single disk for boosting performance and/or protecting from failures. It comes with all the benefits of AHCI mode.
These benefits include less cable size as well as cost, quicker transfer of data via higher rates of signaling, inherent hot swapping, and more efficient transfer via I/O queuing protocol.
Maximum modern SSDs are based on the format of the SATA interface. The latest model is SATA III that reads at 6 Mbps and writes faster than an HDD. Since the invention, three key revisions have occurred for increasing bandwidth and implementing advanced features without changing the connector.
A great thing about SATA is that it is an excellent fit in case of an enterprise-class SATA and a storage device or server with a SAS or SATA host interface.
It is possible to expand the lifespan of the storage device and increase its performance due to its ubiquitous nature.
Due to several manufacturers making SATA drives and their high demand, SATA drives are currently economic SSD drives.
However, just because they are cheaper, it does not mean that they are ideal for all types of users, including enterprises conducting big data analytics.
At present, SATA 6 Gbps facilitates SSDs to achieve an approximate speed of 560 Mbps. Although this may seem quite appreciable, it is yet a limitation. SATA 2.0 is relatively slower with maximum the bandwidth of 280 Mbps.
In case of SSD design, a prime controller uses lanes to reach to NAND chips that store information. Each of these chips has its own speed of performance. Older NAND supported 50 Mbps per chip. Today, a controller uses these chips as if there are several drives in a RAID 0 array.
An increasing number of chips connected to it through lanes facilitates more speed. Thus, the modern NAND chips in SSDs for consumers support 200 Mbps. When used with 4-8 chips, SSD facilitates up to 1.6 Gbps speed. This is why SATA 6 Gbps is now a bottleneck.
Another limitation of a SATA interface is its higher overhead than PCIe 3.0. This is encoding overhead that triggers a loss of 20% bandwidth. Even PCIe 2.0 has this same limitation as SATA 3.0.
However, it ensures 25% more bandwidth. The revised PCIe 3.0, nevertheless, results in a loss of only 1.54% bandwidth.
PCIe is a connector for motherboard expansion. It is typically a slot into which you plug a card such as graphics, sound, RAID, or a network card. It has replaced the former PCI bus standards and has facilitated more elasticity for expansion.
A recent invention in the SSD field is the drive connecting servers and storage series via PCIe. In case of these drives, PCIe is fundamentally the backplane. By bypassing the controllers, the PCIe drives plug directly into the server’s backplane. Here, the speed is higher than that of other SSDs.
PCIe comes with several improvements such as better performance scaling, more comprehensive reporting of errors, smaller footprint, and higher bandwidth. Each PCIe Gen 3 lane is capable of shifting data at 985 Mbps. A few manufacturers are offering storage devices based on 20-lane PCIe. This is super fast, which justifies why PCIe-based SSDs are more in demand than SATA ones when it comes to handling low-latency and bulky content such as videos.
On a motherboard, a physical connector usually supports up to 16 lanes for transferring data. An x4 PCIe device can easily accommodate itself in a PCIe x4 slot or x16 slot. While PCIe 1.0 supports 250 Mbps per lane, PCIe 3.0 facilitates 1 Gbps per lane. However, in reality, it works only up to 985 Mbps because of the enhanced encoding scheme. By multiplying the number of lanes with lane speed, you get maximum speed for that slot.
PCIe comes with interface speeds of a maximum of 1 Gbps per lane, while SATA offers 0.6 Gbps. Therefore, for those who need more speed, PCIe is an ideal choice. More lanes from SATA need an increasing number of SATA devices. However, in case of PCIe, it is possible to scale up the bandwidth in a single device up to 16 lanes.
The modern chipsets offer only up to 1.6-1.7 Gbps in case of SSDs in RAID 0 linked through SATA 3.0. However, in the case of PCIe, the probability of bandwidth throughput is higher (16 lanes x 1 Gbps), which is up to 15.75 Gbps from a single device via PCIe 3.0. Further, it is also possible to use RAID 0 PCIe-based storage devices for enjoying more rapid speed, provided the chipset in use supports it.
Moreover, PCIe ensures less latency and facilitates a direct CPU connection. Conventionally, a SATA controller is indirectly linked to the CPU, as it is first connected to a chipset through which it reaches the processor. However, PCIe connections are direct to the CPU. This is why data flow and processing are faster.
Even SATA drives can link to PCIe backplanes. Nevertheless, the two interfaces unite the form factors of physical hardware with software protocols. This ends up decelerating the data flow. Unlike SATA, data through a PCIe goes both ways simultaneously. This means it is a full-duplex option.
Most interest in PCIe drives is from the consumer market, but an equal response is expected from the enterprises. So, why it is still not in use on a larger or a wider scale? Well, this is because of one catch.
Until now, not much standardization has taken place on how these drives should communicate with the system. Manufacturers, thus, have no choice but to make their own. However, they are totally inclined towards performance instead of compatibility and standardization. Yet, the work of unification has started due to which newer drives are proving themselves better.
Although newer SSDs are introduced, they all seem to be having the same problem of low speed. More advanced SSD controllers are supporting more lanes due to which NAND I/O speeds are boosting significantly. However, still, speed potentials are restricted! Therefore, if the host interface is unable to scale up or adjust to increasing requests, PCIe is the best alternative.
Choosing between these two SSDs is actually a matter of requirements. If you know what you want, it becomes easier to compare both and select the one that best fits your needs as per the set budget. Still, if the budget is low and the demand is a decent SSD connection, a SATA based SSD is reliable. On the other hand, if speed and future-proof system are your requirements, a PCIe based option is better, as it facilitates faster bandwidth and more flexibility.
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