CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [172]
* * *
EXAM TIP SSDs are more dependable as well as more expensive than traditional hard drives. They use less energy overall, have smaller form factors, are noiseless, and use either NAND (nonvolatile flash memory) or SDRAM (volatile “RAM drive”) technology to store and retrieve data. They can retrieve (read) data much faster than typical HDDs. Their write times, on the other hand, are often slower.
Don’t defragment an SSD! Because solid-state drives access data without having to find that data on the surface of a physical disk first, there’s never any reason to defrag one. What’s more, SSDs have a limited (albeit massive) number of read/write operations before they turn into expensive paperweights, and the defragmentation process uses those up greedily.
Connecting SCSI Drives
Connecting SCSI drives requires three things. You must use a controller that works with your drive. You need to set unique SCSI IDs on the controller and the drive. You also need to connect the ribbon cable and power connections properly.
With SCSI, you need to attach the data cable correctly. You can reverse a PATA cable, for example, and nothing happens except the drive doesn’t work. If you reverse a SCSI cable, however, you can seriously damage the drive. Just as with PATA cables, pin 1 on the SCSI data cable must go to pin 1 on both the drive and the host adapter.
BIOS Support: Configuring CMOS and Installing Drivers
Every device in your PC needs BIOS support, and the hard drive controllers are no exception. Motherboards provide support for the ATA hard drive controllers via the system BIOS, but they require configuration in CMOS for the specific hard drives attached. SCSI drives require software drivers or firmware on the host adapter.
In the old days, you had to fire up CMOS and manually enter CHS information whenever you installed a new ATA drive to ensure the system saw the drive. Today, this process takes place, but it’s much more automated. Still, there’s plenty to do in CMOS when you install a new hard drive.
CMOS settings for hard drives vary a lot among motherboards. The following information provides a generic look at the most common settings, but you’ll need to look at your specific motherboard manual to understand all of the options available.
Configuring Controllers
As a first step in configuring controllers, make certain they’re enabled. It’s easy to turn off controllers in CMOS, and many motherboards turn off secondary ATA controllers by default. Scan through your CMOS settings to locate the controller on/off options (see Figure 11-43 for typical settings). This is also the time to check whether your onboard RAID controllers work in both RAID and non-RAID settings.
Figure 11-43 Typical controller settings in CMOS
Autodetection
If the controllers are enabled and the drive is properly connected, the drive should appear in CMOS through a process called autodetection. Autodetection is a powerful and handy feature, but it seems that every CMOS has a different way to manifest it, and how it is manifested may affect how your computer decides which hard drive to try to boot when you start your PC.
One of your hard drives stores the operating system needed when you boot your computer, and your system needs a way to know where to look for this operating system. The traditional BIOS supported a maximum of only four ATA drives on two controllers, called the primary controller and the secondary controller. The BIOS looked for the master drive on the primary controller when the system booted up. If you used only one controller, you used the primary controller. The secondary controller was used for CD-ROMs, DVDs, or other nonbootable drives.
Older CMOS made this clear and easy, as shown in Figure 11-44. When you booted up, the CMOS queried the drives through autodetection,