It may be time for a solid-state disk drive, part 2 – St. George Daily Spectrum

Last week I discussed the two types of communication standards/protocols, SATA and NVMe for solid-state disk drives. Basically, the SATA protocol can be used on almost every computer, but the new NVMe protocol requires a hardware interface that may only be on some recently purchase computers. NVMe protocol supports much faster SSDs, and how to determine if your computer has the hardware interface.
Part 1: It may be time to upgrade your computer with a solid-state disk drive, Part 1
A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage.
The form factor is a key specification. There are plenty of form factors for SSD. This article is going to introduce some main host interface of SSD.
The 3.5-inch desktop HDD form factor offers a range of height options, from 19.9 mm to 26.1 mm. The mobile 2.5-inch HDD form factor ships in heights ranging from 5 mm to 15 mm. Two of the most popular mobile form factors are single-platter 7 mm and dual-platter 9.5 mm.
Many solid-state drives (SSDs) are designed for the HDD mobile 2.5-inch form factor (called the small form). SSDs that fit into the same slots as HDDs generally use the small form SATA interface to transfer data to and from the host computing system. There are many other types of SDD form factors.
1. SATA
SATA is a main interface of SSD. It is designed primarily for interfacing with mechanical hard disk drives (HDDs), but SSD succeeded this kind of interface, too.
2. mSATA
An mSATA has a smaller form factor than a standard SATA SSD and is designed for use with portable, power-constrained devices such as laptops or tablets.
3. SAS
SAS means Serial-Attached SCSI. The most common drive form factors for a SAS SSD are 2.5-inch and 3.5-inch. The latest SAS SSD bandwidth could reach 24Gbps.
What is important to note in the differences is speed and capacity.  The Sata interface is now the most common interface for laptop/desktop computers.  Introduced in 2003, the SATA interface has a maximum speed of 6Gb/sec, and currently has a capacity of 250Gb – 4Tb(4000Gb).
The mSATA interface was introduced in 1986 and has a maximum speed of 2.56Gb/sec, with a maximum capacity 38Gb-73Gb.  This older technology is rarily found, but is used in specialized equipment.  
The SAS interface was introduced in 2004 and has a maximum speed of 24Gb/sec, but has only a maximum capacity 38Gb-300Gb (very high speed, but limited capacity).
Within about 5 years of mass-market mainstream adoption (2005–2010) many SSDs were already held back by the comparatively slow data rates available for hard drives, unlike hard disk drives, some SSDs are limited by the maximum throughput of SATA.
High-end SSDs had been made using the PCIe bus before NVMe, but using non-standard specification interfaces. By standardizing the interface of SSDs, operating systems only need one driver to work with all SSDs adhering to the specification. It also means that each SSD manufacturer does not have to use additional resources to design specific interface drivers. This is similar to how USB mass storage devices are built to follow the USB mass-storage device class specification and work with all computers, with no per-device drivers needed.
There are many form factors of NVMe Solid State Drive, such as AIC, U.2, M.2 etc.
a) PCIe
AIC means add-in card. Almost all early NVMe SSDs are HHHL (Half Height Half Length) or FHHL (Full Height Half Length) AIC, with a PCIe 2.0 or 3.0 interface. Because it has the PCIe interface on itself, a HHHL AIC NVMe SSD is easy to adapt to insert in to the PCIe port of a server or desktop.
b) U.2 (SFF-8639)
SFF-8639, the later name is U.2, is a form factor of NVMe SSDs. When you realize that U.2 is compatible with SAS and SATA (as the below figure shows), it is not surprising that it has a similar name with SAS standard.
Here is an example of U.2 SSD. It is not like the AIC SSD, which is directly inserted into motherboard. U.2 SSD needs a direct-attached cable (DAC) to make a connection with a server, which we talk about later. 
c) M.2
M.2 is another form factor of NVMe SSDs. Compared to U.2 SSDs, M.2 SSD has more flexible physical and modularized specifications, which allows more extensive possibilities. It is what most hardware vendors are now using.
In reality, there are a lot of motherboards that integrate one or more M.2 ports, which means an independent M.2 SSD can be directly inserted into a motherboard.
Now we know about the two communication standards/protocols, SATA and NVMe. We also know the differences between the physical hardware interfaces and the different types of NVMe SSDs interfaces. Next week, I will conclude by discussing the different physical SSD devices with their advantages and disadvantages. This should give you sufficient information when picking an SSD upgrade for your computer. 
Stay protected!
George Cox is the owner of Computer Diagnostics and Repair.  He can be reached at 346-4217.

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