|Mr. Fixit's PC Upgrade and Repair
|Hard Disk Drives
Solid State Drives
The Hard Disk Drive (HDD) is the most important part of any computer. Their capacity range from 256 (MB) to
4 Terabyte (TB). The main hard disk (C:\) is where all software including the Operating System are stored.
Having more than 1 hard disk can be useful. Use one hard disk as your primary disk such as C:\ and the
other hard disk as a DATA drive to store your files, photos, worksheets, etc. You could use multiple hard
disks in whats called a Redundant Array of Independent Disks (RAID). I will explain RAID later. First lets
see the different types of hard disks.
Parallel AT Attachment (PATA) are also known as Enhanced Integrated Drive Electronics
(EIDE). IDEs have been used since 1986 and can be found in todays computers. They have a
16-bit 40-pin connector to interface the hard disk to the South Bridge or I/O Controller Hub (ICH).
These can transfer up 133MB of data per second using a 40-pin/80 conductor cable. It depends
on the type of host controller installed on the motherboard and the drives capability. The
computer will have a primary IDE (IDE 0) and sometimes a secondary (IDE 1) controller which are
labeled on the motherboard. Each controller can connect 2 devices 1 master and 1 slave. Hard
disks connects to the primary while CD/DVD drives connect to the secondary controller. DO NOT
connect a CD/DVD drive on the same controller as the hard disk as this will significantly
decrease performance. The controller will set the speed to the slowest device. In order to have 2
hard disks on the same controller, the primary drive, or boot drive, must be set as 'master' using
the jumpers in the back of the drive next to the IDE connector. The other drive must be set to
'slave'. You can install up to 2 hard disks and 2 CD/DVD drives with this configuration.
Serial AT Attachment (SATA) was introduced in 2000, transferring up to 150MB (1.5 Gb/s) of data per second
compared to IDE's 133MB/s. Parallel was thought to be the fastest way to transfer Data, but discovered at higher speeds
there were more interference or cross-talk between adjacent wires. SATA uses differential non-return to zero signaling,
reducing interference. There are 2 wires for transmitting and 2 wires for receiving. When the drive is idle one wire voltage
is +0.25V and the paired wire is -0.25V. This technique reduces outside interference and cross-talk. SATA drives do not
use the 'master/slave' protocols as did IDEs so there are no jumpers to set. Unlike IDE drives, SATA drives can be
accessed simultaneously giving them a big advantage in performance. SATA became standard in 2003 and replaced IDE
in 2007. Today, there are 3 Versions: SATA I transfers 150MB/s (1.5Gb/s), SATA II transfers 300MB/s (3Gb/s), and SATA
III transfers 600MB/s (6Gb/s).
Introduced in 2013, SATA version 3.2 became the latest revision in the SATA technology known as SATA Express. It is
able to transfer data up to 2GB/s using PCIe lanes. The revision was focused primarily for use with Solid-state drives.
The revision provides motherboard manufacturers 3 options: Legacy SATA is compatible with standard SATA drives, SATA Express using the Advanced Host
Controller Interface (AHCI) is used for PCIe SSD but only provides standard performance using the AHCI driver, and the SATA Express using the Non-Volatile
Memory Host Controller Interface (NVMHCI) to provide High Performance for PCIe SSDs due to their low latency, data transfers with fewer stages, greater
depth of command queues and more efficient interrupts processing.
SSD is around $0.45/GB where as HDDs average just $0.08/GB. NAND SSDs also suffer from performance degradation the longer the
drive is used. This is a phenomenon known as write-amplification, where the actual amount of physical information written is a multiple of
the logical amount intended to be written. Because flash memory must be erased before it can be rewritten, the process to perform these
operations results in moving (or rewriting) user data and metadata more than once.