ModCrash SSD Buyers Guide

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SSD Terminology

SLC

  • SLC stands for Single Level Cell and is a memory element capable of storing a single bit of data. For FLASH memory, this provides lower data density in a component than MLC but it offers a low error.

MLC

  • MLC stand for Multi Level Cell and is a memory element capable of storing more than a single bit of data. For FLASH memory, this provides higher data density in a component but this also increases the bit error rate forcing more sophisticated firmware techniques to be created to deal with the errors. The alternative is SLC.

TRIM

  • A computer command used by a SSD to inform it of data blocks in the SSD memory space that are no longer in use. This command allows the SSD controller to reorganize the memory space it is managing to allow any unused space to be optimally relocated. The TRIM command is intended to become part of the AT Attachment interface standard.

IOPS

  • IOPS (pronounced as “eye-ops”) stands for input/output operations per second. Basically, IOPS is the most common performance measurement used for storage devices, such as hard disk drives (which we know as HDD) and solid state drives (SSD). Basically, IOPS show us the maximum number of reads and writes to non-contiguous storage locations. What does it mean for you? It means that the highest IOPS equals to the highest performance.

Controller

  • The flash controller or just controller is a microprocessor in the SSD that basically is the in between for the SSD drive and host device (PC, external drive, ect.). The controller will manage the file directory of the SSD, error correction, and garbage collection.

Sequential Read

  • A method to benchmark an SSD by accessing large amount of data contiguously.

Sequential Write

  • A method to benchmark an SSD by writing large amounts of data contiguously.

Random Read

  • A method to benchmark an SSD by accessing a certain amount of data.

Random Write

  • A method to benchmark an SSD by writing a certain amount of data.

TRIM

  • TRIM is a SATA interface command that tells the SSD which data it can erase. Basically this command lets your OS tell your SSD that to certain files or pages can be overwritten or erased.

Garbage Collection

  • Process that the storage controller uses to free up space to write data to before it is needed.

AHCI

  • AHCI stands for Advanced Host Controller Interface.

Different Types of SSDs

SSD

  • Solid State Drive that uses non-volatile (RAM is volatile)  memory to store data the same as a hard disk drive.

Hybrid SSD

  • Hybrid SSDs combine both conventional HDD technology with SSD technology to increase speed and space in a cost-effective manner.

PCIe SSD

  • PCIe SSDs are cards that instead of using SATA connection to a host device take advantage of your PCIe. This increases the speed at which the SSD can operate since PCIe lanes are point to point architecture that connects directly to a host instead of sharing a bus.
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