Hard Drive Technology

Table of Contents

Hard Drive Technology .................................................................................................................... 2

Traditional Hard Drive ..................................................................................................................... 3

Rotation........................................................................................................................................... 4

RPM Concern .................................................................................................................................. 6

Cooling the Drive............................................................................................................................. 7

Traditional Hard Drive Issues .......................................................................................................... 8

Solid-State Drive (SSD) .................................................................................................................. 10

Solid-State Drive Flash .................................................................................................................. 12

RAID ............................................................................................................................................... 14

Notices .......................................................................................................................................... 16

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Hard Drive Technology

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Hard Drive Technology

**030 All right. In this module, we'll talk about hard drive technology, the various types.

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Traditional Hard Drive

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Traditional Hard Drive

Data storage device Stores massive amounts of digital information

Components Magnetized aluminum platters Read/Write heads retrieve data and load into RAM

**031 So, traditional hard drives are data storage devices designed to store massive amounts of information. We can't store a lot in RAM, we can't store a lot in static on the motherboard. These are all small, short-term solutions for storing memory, so hard disk is our solution for being able to read/write data on a large scale. Floppies were too small to be able to hold a lot. CD-ROMs were write-once for the most part, even the rewritables. It takes a while to write to them and being able to reuse them. They're made up of magnetized aluminum platters. The standard

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hard drive is very mechanical with read and write heads that retrieve data and load into RAM. Think of it like a record player.

Rotation

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Rotation

The level of performance in hard drives is determined by the spindle speed.

Spindle speed is measured by Revolutions per Minute (RPM).

The more RPM the better the performance.

Common speeds include 5400 RPM 7200 RPM 10,000 RPM 15,000 RPM

Istockphoto.com

**032 So, as the record turns or the platter turns, the speed that it turns at is measured in rotations per minute. So the faster it turns, the faster that that head-- which you can see in this picture-- think of again like the needle on a record player-- can read data off the disk. So you get better performance out of a faster disk. The common one for desktops is 7200 RPMs, 7200 rotations per minute. Laptops a lot of times will

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come with hard drives that are 5400 RPMs because even though they're slower, by virtue of them being slower they also use less power, which is good for portable devices. So we want slower, and you're not using the desktop to do high video editing or any kind of high performance, so the tradeoff-- you'd rather have the power than the performance. The tradeoff. Ten thousand and 15 thousand RPMs are more likely to be seen in servers or high-end workstations that would be used for audio and video editing, for instance.

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RPM Concern

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RPM Concern

A drive that is running too many RPMs can cause the system to overheat.

More common to happen in cases that do not contain very much space

**033 Just like with almost everything in computers, heat is always an issue. The faster the drive, the bigger the heat concerns. So you'll see high-end drives will have heat sinks on them if they're super fast, to avoid them from overheating. You can also buy a cooler fan specifically for hard drives that will fit around them in the bay if they're overheating.

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Cooling the Drive

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Cooling the Drive

Like other system components, drives can be cooled down with a few simple solutions.

Installing drive bay fans Air Flow is key, remove any obstructions

Moving the components to a larger case

Consider reverting back to a slower drive if cost is an issue.

**034 You can install additional fans in the bays, like I just mentioned. Might be the case is too small so the heat's building up and has nowhere to go.

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Traditional Hard Drive Issues

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Traditional Hard Drive Issues

Takes time to spin up

Requires an great deal of power

Creates an abundance of heat

Wear and Tear

**035 Traditional problems with hard drive. It takes to spin up. Again, it's mechanical, so when you first turn on the computer and it gets power, you got to wait for the hard drive to finish spinning up and getting up to that initial speed, kind of like getting up to 55 miles an hour in a car-- you're not going to be right at 55; you have to work your way up to 55. Same thing with a hard drive. It's got to reach up to its speed. Now, we're not talking the same amount of time a car would take; it's quite a bit faster in reaching its speed. But that's still a delay, so it can't read or write until it gets up to that operating speed, so that's

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something you got to wait for, so that can be a delay in booting your system because you got to wait till that comes up before you can do anything. In some servers, there's been issues where if you have too many hard drives, all of them trying to spin up at once can be too great a pull because all of them are going to pull all the power requirements from the power supply at the same time. So in that case, a lot of times in the BIOS you can set delay spin-ups that says, "Okay, this hard drive spins up first; this one waits two seconds and then tries to spin up; this one waits four seconds; this one waits six seconds. So it may take you maybe 30 seconds to get all your drives, if it's a big file server, but it avoids that huge load and draw on the power supply at first boot. So that's something to be aware of. And you even see that often sometimes in regular desktop PCs where you can delay the spin-up of a hard drive. And they're susceptible to wear and tear. I know personally you got to be very careful with them because you're talking little needles, magnets, on a head-- think of it just like a record player. Just like a record, they can scratch very easily. And although you can't actually see those heads, the case falling over on its side is enough sometimes just to damage the head, and that means the head's going to hit the plate and that's going to cause a scratch. And just like in a CD or record, if you

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cause a scratch on the platter, that can cause damage to be lost, and permanent damage also. And since it's mechanical, it's subject to wear and tear, especially over time, if being used a lot. You got to be aware that, "Oh, this drive's been used for five years straight. I probably should replace it just because of wear and tear with mechanical stuff."

Solid-State Drive (SSD)

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Solid-State Drive (SSD)

Developed to solve all issues attached with platter-based drives

Uses memory chips as a replacement for the revolving parts used in platter-based technology

Powered by a combination of current and positive/negative charges

Composed of Semiconductors Transistors Bubble memory

Pcifilerecovery.net

**036 So then along came solid state drives. Think of solid state drives kind of like USB flash drives but faster. So instead of being mechanical, it's all electronic. It's

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memory chips that can save data after power's lost-- so kind of the best of both worlds. They're bigger than RAM but they also save the data, unlike RAM; when you lose power, all the data is gone. So all those issues we were just talking about with heat and about wear and tear and the platters and the heads hitting the platters and stuff-- all those problems are gone with SSD because we don't have any mechanical parts anymore. It's all just memory chips. Specifically bubble memory.

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Solid-State Drive Flash

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Solid-State Drive Flash

Can also use nonvolatile flash memory NAND Type of Flash memory

Delivers rapid read/write execution

Disadvantages More expensive than traditional hard drives Faster read, but slower write Durability

Erases large amount of data before it can rewrite which builds more resistance on transistors eventually causing the SSD to transform into a read only state

**037 Some of the advantages of SSDs are that they are faster to read, but slower to write. So a common practice when using SSDs in a desktop environment is put your operating system on the SSD drive, because that drive's fast at reading and your operating system files don't change often-- so put your operating system on the SSD, and then put all your other data files, like any videos and music and other large files, on a mechanical drive, because mechanical drives are cheaper than SSD also. SSDs are still rather expensive.

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So if you're doing a lot of stuff that's read-only, put that on the SSD. And that's a pretty common practice in desktop computers right now, because you'll really notice a difference that when you boot off an SSD drive with your operating system it is incredibly fast. Besides the cost though, it produces less heat and it pulls less power too, so it's very energy efficient because there's no moving mechanical parts. Durability-- it does have a shorter theoretical lifetime than a mechanical drive because of how many times you can rewrite to the memory, but it's not that large of a concern unless you were using it in a heavy write environment like maybe a database, which it wouldn't be optimal for anyways because they're not good for write; they're better for read. The technology would probably be outdated before you would actually reach the limit of an SSDs number of rewrites. Kind of like CD-RWs theoretically have a limit to how many times you rewrite on them, but I've never used a CD-RW that many times to get to the theoretical max.

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RAID

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RAID

Redundant Array of Independent discs (RAID) uses multiple Disks to store data and achieve redundancy.

Hardware-based Needs a RAID controller to interface the host with the storage discs

o Controller is responsible for the management of the discs and calculation of parity bits

Allows for hot-swappable discs for data recovery without downtime Software-based

Handled by the operating system through the normal drive controller Can be faster than hardware-based RAID, but at the expense of CPU

performance Used for high-transaction volume systems and online transaction

processing Entire system must be rebooted after a failure Cannot provide redundancy to boot volume (some exception for RAID-

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**038 Another kind of disk technology is RAIDs-- Redundant Array of Independent Disks. It uses multiple disks to store data and achieve redundancy. There's two kinds of common types of RAID. We have the hardware-based where it's done through, at the BIOS level, through either actually sitting on the motherboard or sitting through an add-on card that provides RAID capabilities. When it's at the hardware level, if I do a RAID-0, which is two disks striped to look like one drive, it's going to look like one drive to the OS and everything else is going to be handled by the hardware.

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So only the BIOS is going to know it's actually two drives; the OS has no idea it's a RAID. Now, software-based lets you have a few more options, but that's done at the OS level. And the problem with that is you can lose-- if the OS gets lost for some reason, you also lose all your data about your RAID, which could cause problems. Especially if you're doing a stripe, you might lose the information about the two drives being together and you won't be able to pull it off because the information that contained the correlation between the two drives were saved in the OS and not at the BIOS, and that the BIOS is kind of safer at the hardware level. Software RAIDs are cheaper and easier to implement, though. They don't require any additional hardware. But also since they're not using additional hardware, they're taking more of a toll on the CPU of the system instead of having its own dedicated hardware to do that RAID functionality. And if it's at the software level, it can also not provide redundancy to boot volume because it's part of the boot volume of the OS.

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Notices

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Notices 2014 Carnegie Mellon University

This material is distributed by the Software Engineering Institute (SEI) only to course attendees for their own individual study.

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Hard Drive TechnologyTable of ContentsHard Drive TechnologyTraditional Hard DriveRotationRPM ConcernCooling the DriveTraditional Hard Drive IssuesSolid-State Drive (SSD)Solid-State Drive FlashRAIDNotices