Instructor: In this lesson,
we're going to talk about hard disk drives,
also called HDDs.
Now hard disk drives are a form of mass storage device,
and mass storage devices
are simply any kind of non-volatile storage device
that can hold data when the system is powered down,
at a large scale.
This is why we call it a mass storage device.
Generally, these are going to be measured not in megabytes
but in gigabytes or terabytes.
When dealing with mass storage devices,
these are generally categorized into two different types:
internal and external.
When you're dealing with an internal device,
this is the device that's going to be placed
inside of your computer's case or tower.
Generally, this is going to include things
like hard dish drives, solid state devices,
optical drives, tape backup drives,
and old-school floppy dish drives.
On the other hand,
we also have some mass storage devices
that are considered external devices.
These are things that are going to exist
outside of the computer's tower or case
and are going to be connected to an external port
on that case.
For example, you might have an external USB hard drive
or an eSATA drive
that you'd be able to connect and be able to access the data
using a port on the outside of your computer.
Now when it comes to mass storage devices,
there are generally three sizes of devices.
We have a 2.5 inch drive, a 3.5 inch drive,
and a 5.25 inch drive.
The 2.5 inch drive and the 3.5 inch drive
are normally going to be reserved for internal hard dish drives
as well as solid state devices,
whereas the 5.25 inch drive bay
is going to be reserved for optical drives,
tape backup drives,
and old-school floppy dish drives.
Now depending on your case,
you'll have a certain number of these different bays
in these different sizes.
If you don't have enough of the smaller bays,
you can always use an adapter
to put a smaller device into a larger bay.
For example, you can mount a 2.5 inch drive
into a 3.5 inch caddy
and then place it into the 3.5 inch bay.
All right, now that we understand the basics
of mass storage devices,
let's focus in specifically on hard dish drives
for the rest of this lesson.
Now a hard dish drive is a device that's going to store data
on a metal or glass platter
that is coded with a magnetic substance.
This magnetic substance can then be charged
with different electrical currents
to be able to create data on those
by storing 1s and 0s on that magnetic substance.
Now this is going to be done on these platters,
and these platters are going to be accessed
using a read/write head.
This is actually moved
by what's known as an actuator mechanism.
So if you think about an old-school record player,
it works similar to that.
The platter is going to spin around,
and as you want to read information from that platter,
you have to have that actuator arm in the write position
so as it moves forward and back across that platter,
that read and write head
can then read different parts of the drive.
Because of this,
if you have data stored on the inside of the drive
or the outside of the drive,
there is going to be a different seek time
to be able to find that data
based on how far the actuator has to move
and how much the read/write head has to move
up and down the actuator itself.
Now when you look at this platter,
it's actually going to be logically divided
into things known as tracks and sectors.
Tracks are essentially one circle going around that platter
and the sectors are going to be a chunk
of that particular track.
Now, each of the sectors is going to have a width
of about 512 bites,
and each of the tracks is going to be a different size
based on the drive geometry that was created
when the low level formatting
was conducted by the drive's manufacturer.
So as you can see,
we need to spin this platter around
to be able to move the actuator and the read/write head
to the right location to read the data.
This is called seeking or retrieving the data.
Now, because of this,
the faster you can spin a hard drive,
the faster you can actually access the data
that's being stored in it.
So when you're trying to buy a hard drive,
you need to consider its speed
as measured in RPMs, or revolutions per minute,
because the higher speed
is going to give you better drive performance.
Now, when you look at a hard drive,
you're going to see generally four basic types of speeds
that are out there.
The first is 5400 RPM.
This is the slowest model of hard drives that are out there,
and this is what you're going to find in budget
or low-end workstations and PCs.
The second one we have is known as 7200 RPM.
This provides us faster performance
while not having an exceptionally high cost.
This is a good balance
and it's used in most modern computers
when you purchase one with a hard drive.
The third one we have is known as 10,000 RPMs,
and this is where we start getting
into the high-performance drives.
Generally, these will cost more money
than the 7200 RPM drives
but they do give you increased performance,
and they're used a lot with gaming PCs,
high-performance PCs and servers.
And finally, we have 15,000 RPMs.
Now 15,000 RPMs is one of the highest RPMs
you're going to see used inside of a hard drive.
Now because of this,
it does have an extremely high cost
but it does give you great performance.
Now in general, you're not going to see a lot
of 15,000 RPM hard drives being used,
and the reason is by the time you start getting
to that level of hard drive,
you could have bought a solid state device
which eliminates a lot of these seek time issues
because SSDs don't have moving parts
like these traditional hard drives.
So you may be wondering
why do people like to use hard drives
instead of using a solid state device.
Well, mainly, it comes down to cost and not performance.
For performance,
solid state devices are going to be so much faster
than a traditional hard drive,
but a hard drive is a lot cheaper to produce.
And so you can get a much larger capacity hard drive
for the same cost as a very low capacity solid state device.
For example, I recently installed a solid state device
into a new computer.
This solid state device was 2 terabytes in size
and it cost me around $250.
Now, if I had instead used a 7200 RPM hard drive,
I could have gotten a 12 terabyte drive for that same $250,
given me six times more storage.
So there is still a place for hard drives.
In a lot of systems,
people will put both in,
and that's what I ended up doing with my computer.
I put in a solid state device, which is much faster,
for my primary operating system and application files,
and then I installed a hard drive,
that was a very large capacity drive,
to be able to store all the excess files
such as videos that I create for things like this course,
because those are huge file sizes
and it takes up a lot of disk space to hold those,
and if I use solid state devices for everything,
it would be extremely expensive.
So when you're looking at a hard disk drive,
another area you need to consider is its buffer size.
Now, the buffer size is going to be internal buffer or cache
on that hard disk drive
that's going to be able to cache a lot of the data
to increase your performance.
The typical buffer size here
is going to be anywhere from 8 megabytes to 256 megabytes
depending on the drive you buy.
When it comes to buffer size,
the larger the buffer, the better the performance
so you want to pick a hard drive
that has a large buffer size when you're picking out one
if performance is a main concern for you.
When it comes to installing your hard disk drive,
you're going to have to connect it to your motherboard
using some sort of a cable,
and this is going to depend
on the form factor of your motherboard
as well as the hard drive that you select.
In most modern systems,
you're going to be using a SATA cable
to connect your hard disk drive to your motherboard,
and this can be either SATA version 1,
SATA version 2, or SATA version 3.
When using a SATA connector,
you're going to be using two cables,
one which is a 7-pin data connector
that is an L-shape cable,
and another that is a 15-pin power cable
that again is an L-shape connector.
When you look at SATA version 1,
this is going to have a maximum speed
of 1.5 gigabits per second
which gives you about 150 megabytes per second
of throughput,
or you can use SATA version 2,
which has a maximum speed of 3 gigabits per second
which translates roughly to about 300 megabytes per second
of throughput,
or SATA version 3,
which is the most modern and fastest version of SATA
which is rate at 6 gigabits per second
or about 600 megabytes per second of throughput.
If you're working on a legacy system,
you may come across an IDE or PATA interface
instead of using a SATA interface.
For these devices, you'll use a 40 wire data cable,
which is a flat ribbon cable,
to be able to connect the motherboard to the drive,
and then you'll use a 4-pin Molex connector
to be able to power that drive,
or you can use an 80 wire cable
that combines the data and power into a single cable
if your motherboard supports it.
As I said, this is more of a legacy item
so you're not likely to see this in most modern computers,
but if you're working in a corporate
or enterprise environment
and they have some older systems lying around
like critical servers or SCADA workstations,
you may come across this type of interface.
The third type of interface you might find on a hard drive
is a SCSI interface,
which is written SCSI or small computer systems interface.
Now, when you're using a SCSI cable,
this can either support 7 or 15 devices in a daisy chain
depending on if you're using narrow SCSI or wide SCSI,
and each device does require a device ID that's set
so on that cable,
each device knows what number it is
between 1 and 7 or between 1 and 15.
To configure your device
to know what number it's going to be assigned,
you're going to set this using a jumper block
or selector switches
on the back of that device.
In modern systems,
SCSI is considered to be a slow speed interface
because narrow SCSI
can only operate at 40 megabits per second
and wide SCSI can only operate at 320 megabits per second.
And so SATA is much more popular
because of its higher speeds
and it is used a lot more often than SCSI in modern systems.
So as you can see,
hard disk drives are still alive and well
in most modern computers,
but they are going to be using SATA
instead of IDE, PATA, or SCSI.
When you're trying to decide
whether or not to use a solid state device
or a hard disk drive,
this is normally going to come down to three factors:
cost, performance, and capacity.
This is because hard dish drives cost a lot less
than a solid state device
but they also have less performance
than a solid state device.
Now the big benefit of using a hard drive
over a solid state device
is the fact that they have larger capacities for storage,
and normally, you'll be able to get 5, 10, or even 15 times
as much storage on a hard disk drive
for the same cost as the equivalent solid state device.