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How to Choose a Storage Device?

By Benjamin Wieberg - Edited by James Baker - Illustrations by Mansen Lin

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Introduction
There are multiple devices which are used for storing information for computers. The most important of these is the hard drive or solid state drive, which is used in the computer to store the operating system and give the computer something to boot from. There are five storage types, including Hard Drives, External Hard Drives, USB Flash Drives, NAS (Network Attached Storage), and Optical Disk Storage. I will discuss all the options for storage in this article.

Hard Drives
Hard drives are the first and primary choice for storage. Hard drives are installed inside the computer and in typical cases have the operating system installed on them and are used as the main source of storage. In some rare cases people have them outside the computer in an enclosure and boot from them externally. Hard drives have five different connections which are SCSI 320 & 160, SAS, SATA, and IDE. Hard drives range in sizes from 40GB to 2TB (GB meaning gigabyte and TB meaning terabyte). Determining the size of the drive needed is dependent on the amount of information you want to be able to store. In some cases one hard drive isn�t enough, so multiple hard drives are used together in a manner which allows more than one drive to be used simultaneously as a single unit, called RAID (Redundant Array of Independent Disks). Raiding is the act of chaining hard drives together to either increase performance, or increase redundancy and reliability. A hard drive RAID set can only be achieved when using 2 or more of the same drive. This generally means same size, speed, and brand. To help you understand this better I shall discuss each standard raid option.

Raid 0
-Raid 0, or striping, increases performance at the expense of redundancy. With raid 0 you have 2 or more drives linked together in which the system sees them as one big hard drive and writes to all of them simultaneously allowing for a faster transfer of data. For example, you may have two drives, each one 500GB. When put in raid 0, instead of seeing two 500GB drives they are seen as a single 1TB hard drive. When you copy or install something to the hard drive, instead of writing to one 500GB drive, it splits the data in half and writes each half to a different drive at the same time. This way the read and seek time of files is reduced because it reads from both drives together allowing for quicker data access. However, just like with a single drive when a drive goes bad you lose everything. There are a few exceptions with a single drive in which you can recover the data, but with raid 0 this is not the case. Since data is split between two drives you lose the ability to recover the data.

Raid 1
-Raid 1 (also known as a mirror raid) is the act of chaining two or more hard drives together in which the first drive is cloned or copied to the other disks. Raid 1 is not for performance, but for redundancy. Raid 1 is more useful for systems in which data is crucial and cannot be lost. For example, in a raid 1 setup with the same two 500GB drives, your computer will only see 500GB. However, when it writes to one of the hard drives, it will make an exact copy of the data to the second hard drive. This way, if one drive fails in the future, you can swap to the second one and still boot like it�s the first drive. At that point you will need to replace the bad hard drive, or when the second one goes out you will lose all your data.
Raid 5
Raid 5 is a stripe with parity raid in which the data is spread across all the drives, with a section of each drive used for parity data. However, in raid 5 - unlike raid 1 - you keep more of your data storage space. In raid 1, if you have two drives, the computer will only see one. In raid 5, three drives is the minimum, although 4 or more are also commonly used. Say we have 3 of the 500GB drives from earlier. In raid 1, you would see 500GB, and then it would be mirrored to the other two. In raid 5, you would see 1TB of storage and the data would be spread across all three drives. The other 500GB is not lost, but is used for storage of the parity data. Parity data allows for the rebuilding of a raid array in the case a drive goes bad. For example, if a raid 5 array of 3 drives has one drive fail, the computer can still access and rebuild all the data due to the distributed parity data on the other two drives. Replacing the failed drive would allow you to rebuild the original contents of the drive, and the array will function normally.

Raid 6
Raid 6 is similar to raid 5 in that it is a stripe with distributed parity. The difference is that you now have twice the amount of parity data, and a minimum of four drives is required to assemble a raid 6 array. You also lose an extra drive�s worth of capacity, but you can lose up to two hard drives and still rebuild the array, instead of the one drive failure limit in raid 5. Raid 6 is common in larger arrays of 6 drives or more, where the probability of multiple simultaneous drive failure is higher than an array of fewer disks.

External Hard Drives
External hard drives are exactly what they sound like: drives which are stored outside the computer, and most of the time are used for transferring data to other computers or store information you need both at work and at home. External hard drives consist of either a 3.5 or 2.5 inch hard drive which is stored in an enclosure, which in some cases requires an alternate power. Most of the time power is supplied to the hard drive through the USB connection. Some people are under the assumption that you can only purchase an external hard drive pre-assembled, but this is incorrect. In fact, it is sometimes cheaper to buy the desired hard drive and a fitting enclosure and assemble it yourself. A lot of people buy external drives for their mobility; in this case the best choice is a 2.5 inch hard drive with a matching enclosure. However, if it is going to be stored in one place it might be cheaper to get a 3.5 inch hard drive and a matching enclosure.

USB Flash Drives
USB devices are ultra portable devices about the size of a key on your keychain which allow you to store and transfer files. The capacities range from the ultra-small, such as 16MB, to larger 64GB capacities. These devices plug into the USB port on your computer and are supplied power through the USB port. USB flash drives use flash memory which allows for data to be stored without any moving parts. USB flash drives are accessed and used in the same manner as external hard drives, while providing high portaiblity.

NAS
NAS or Network Attached Storage is standalone system that allows a single hard drive or multiple drives in RAID to be accessed via a network connection. NAS devices are great for use in situations where files need to be stored in a common location for access by multiple users. Unlike USB flash drives and external hard drives, NAS devices are not normally meant to be portable devices.

Optical Disk Storage
Optical disks are circular disks capable of containing audio, video, and data files. There are four types of disk drives that are commonly known right now and they are Compact Disk or CD, DVD, HD DVD, and Blue Ray. Each has different capacities which they can hold and depending on what size the file is your trying to store depends on the disk you should use. However, these disks can only be used if you have the appropriate drive to write to the disks.

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