CompTIA A+ Exam Prep: Understanding Storage
Storage devices and backup media are essentially devices in which you can store and retrieve data. There are many different types of data storage devices, and in this article we will focus on the ones you’ll need to know for the 2009 CompTIA A+ Exam.
While the 2009 and 2006 exams are very similar, a few new items have been added to the newly revised exam. Solid State Drives (as primary storage) have been added to the updated exam, as well as Blu-Ray drives, and the differences between Hot-Swappable and Non-Hot Swappable devices.
In this article you’ll learn about:
- Floppy Disk Drives
- Hard Disk Drives
- Solid State Disks
- Optical Drives
- Removable Storage
- Hot Swappable vs. Non-Hot Swappable Drives
• Floppy Disk Drives
A Floppy Disk Drive (FDD,) is an older storage medium in which data is written onto a thin magnetic disc within a plastic enclosure. FDDs have evolved from a large 8-inch version, to 5 ¼-inch, and finally to the 3 ½-inch version available today.
The most common 3 ½-inch floppy disk can hold 1.44MB of data but variations such as ZIP drives can hold much more. FDDs today are considered legacy equipment, and although they do still serve some purpose, their usage has been largely replaced by newer storage mediums such as USB Flash Drives, CDs, DVDs, and others.
• Hard Disk Drives
On the 2006 A+ Exam, you would be expected to know that a Hard Disk Drive (HDD) was a device which stores data on rotating platters with magnetic surfaces. However, with the introduction of Solid State Drives (SSD,) this is no longer necessarily true. Yes, a HDD is what I described above, but now, so are SSDs. The 2009 exam has been updated to reflect that.
HDDs are most commonly seen between two form factors, a 3.5-inch form factor used in most desktop computers, and a 2.5-inch form factor commonly used in laptops and netbooks. There are also 5.25-inch, 1.8-inch, 1.3-inch, 1-inch, and 0.85-inch HDDs, but these are rare and usually used in specialized circumstances.
Capacity has greatly changed since the introduction of HDDs. 3.5-inch drives can have a total capacity of up to 2TB of space, while 2.5-inch drives can reach 1TB of space.
There are also two types of connectors used with 2.5-inch and 3.5-inch drives. Parallel ATA, Integrated Drive Electronics, and Enhanced Integrated Drive Electronics (PATA, IDE or EIDE) drives use 40-pin connectors and have a max data transfer rate of 133MB/s (originally 16MB/s.) Serial ATA (SATA) connectors were designed to replace the older PATA connector and use a much smaller connector and cable, using only 16 data conductors and reaching speeds of up to 6Gbit/s (originally 1.5Gbit/s.)
• Solid State Disks
Solid State Disks (SDDs,) are very similar to HDDs and even emulate the same interface so that they are easily integrated. A SSD is used just as a HDD is used, except rather than use magnetic plates to store information (data) they use flash memory to store data.
Using flash memory to store data has many advantages over the spinning magnetic plates found in HDDs. For example, since there are no moving parts, they can withstand more movement, shock, high altitude, vibration, etc. without as much of a risk of damaging the unit; they are completely silent, and without having to wait for spin-ups and other mechanical delays, they are much faster than HDDs (about 200-250MB/s.)
However, they are also much more expensive than standard HDDs. SSDs also have a much lower capacity compared to HDDs, though they are growing quickly, the current max capacity is 256GB, compared to the maximum HDD capacity of 2TB.
• Optical Drives
There are a few types of optical drives on the market today. CD drives are used primarily to read audio and data CDs. Although there are variations, CDs can hold a maximum of 700MB or 80 minutes of audio per disc.
DVD drives are similar, except CDs are replaced with DVDs. A DVD is an optical disc that can typically hold 4.7GB of data, however, double layer and double sided DVDs have been released, raising the maximum size from 4.7GB to about 17GB (double-sided, double-layer.) DVDs are used primarily as video discs however, they are also used in other formats such as High Definition audio storage, data storage, and as game discs (Xbox, PS2, Wii, and Xbox 360.)
Rewritable (or RW) discs are either CDs or DVDs that not only allow you to write data to them, but also rewrite data to them. Most discs can be rewritten up to about 1000 times. RW discs that support Random Write Access (such as DVD+RW) even allow you to add or remove data from a disc without erasing the entire disc and starting over.
The newest addition on the 2009 exam, in terms of optical media, are Blu-Ray discs (BD.) Blu-Ray Discs were designed in direct competition with HD DVD discs to supersede the DVD format. Eventually HD DVDs were no longer produced and BDs were chosen to become the dominating new DVD format.
BDs can hold up to 25GB on a single-layer disc and 50GB of a dual-layer disc, meaning much higher quality video and audio can be stored on the discs. The main reason more data can be stored is the laser that is used. DVDs use a red laser, and BDs use a blue-violet laser with a shorter wavelength, allowing for 5-6 times more capacity than on DVDs.
• Removable Storage
There are many types of removable storage. Tape drives are plastic or metal enclosures holding streaming magnetic tape. A cassette tape or VHS tape is a type of Tape Drive. Tape Drives provide sequential access storage meaning, in order to read certain data, it must constantly rewind or fast forward to the correct location of the data. However, even though they have a very slow seek time they can stream data extremely quickly. According to Wikipedia, modern drives can reach continuous data transfer rates of up to 80MB/s, which is as fast as most 10,000 RPM HDDs.
A Flash Drive (also referred to as a Jump Drive or Thumb Drive) is a flash memory device with a USB connector built in. Flash Drives have been one of the major factors resulting in the removal of floppy drives from modern computers. Because of their small size, fast speed, ease of use, and high capacity (currently at a maximum of 256GB,) flash drives are the preferred data storage devices for the average consumer.
Secure Digital (SD) cards have a maximum capacity of 4GB however, SD High Capacity (SDHC) cards have raised this capacity cap to 32GB. And the recently announced SD eXtended Capacity (SDXC) cards will allow for up to 2TB of storage on a single card.
There are also three common form factors when it comes to SD cards:
- SD, which is the full size card, is 32mm at its longest side;
- MiniSD is the second smallest form factor, and is 21.5mm at its longest;
- MicroSD is about as large as a fingernail, and is only 15mm at its longest.
External USB Drives are connector interfaces in the form of either cables or enclosures that connect to your computer or device through a USB port. Most commonly you can find External USB Drives in the form of either HDDs or CD/DVD Drives. These are exactly the same as the internal drives, except that they are external and connect through USB rather than PATA, SATA, or otherwise.
• Hot Swappable vs. Non-Hot Swappable Devices
Hot swappable devices are devices you can remove from a computer system without interrupting its operation — this is the key difference between hot swappable and non-hot swappable drives.
The most common hot swappable interface is USB. You can simply eject the current device and/or unplug a USB device without having to shut down the system.
Other examples of devices that have hot swappable variations can range from Hard Drives, CD/DVD/BD Drives, PC and Server components, and more.
On the other hand, a non-hot swappable device requires that you shut off your computer before removing or adding the device. For example, an internal hard drive is considered a non-hot swappable storage device because you can’t add it or remove it with your computer being on.
While there is a lot of overlap in storage information on the 2006 and 2009 A+ exams, the 2009 exam will put a bit more focus on the new technologies, especially the ones that have been added to the exam objectives.
So when studying for your exam, remember what I mentioned before about understanding the differences between hot swappable and non-hot swappable devices, solid state drives as primary storage and Blu-Ray drives.
Also make sure that you thoroughly understand what these storage devices are capable of and how they can be used. Some of the questions on the A+ exam can be very detailed.
Good luck on your exam and make sure to check out my article about what you need to know about RAM for your A+ 2009 Exam.