3.8 Partitions

Posted Dec 10, 2025 Updated Jan 12, 2026

By So Hee Park 20 min read

✅ Partitions and Harddisk

in secondary memory = hard disk
the plates can use the two sides at the same time
so one header per one side
in total, two headers
plates rotate using spindle motor
header does not move

✔️ Track circle

concentric circles called Track circle
outmost circle is 0
as you go inside, the number of the circle increses 1, 2, 3...

✔️ Sectors

the circles are divided into sectors
the triangles goes from 12 o’ clock : sector 0
it turns like the clock direction

✔️ Unit

intersection of track and sector
all unites save the same bytes, although in the picture, size looks different
no matter distance to the center
The external units and internal units save the same bytes
The internal units have more information compressed
this means the information stored in internal units are more safe

✔️ Unit 0

intersection of sector 0 and circle 0
⭐️ unit 0 stores the booting system of my disk
😭 if we damage unit 0, the disk is useless, as we cannot run the booting system
also the key of transparent encryption in linux is stored in Unit 0
But modern disks have a copy of unit 0 in the interior unit of the last disk
👍🏻 so more difficult to break, and more safer
where: external circle and right next to 12’o clock

✔️ Rest of the units

rest of the units are called just units, they are not numbered

✔️ Two technology of disks

Magnetic technology disk
old
the headers are magnetic
and the tracks had magnetic material
⭐️ if you use magnetic tech, in each of the unit, you can store 512Bytes, if the units are old
magnetic ➡️ 512Bytes per unit
Optical technology disk
new
headers are lazer
tracks are valleys(lazer is kept, 0) and hills(lazer is reflected, 1)
⭐️ 2048Bytes if new (🆚 4times more than magnetic disk)
optical disks keep much more data than magnetic disk
optical ➡️ 2048Bytes per unit
the size of bytes you can store per unit does not change on the size of the disk
as disk is a circle shape, external units are bigger, but the amount of bytes we can save is the same
the ones interior the disk the bits are more compressed, but save the same bytes
👉🏻 if you want to hide the information, save it in interior, compressed
👉🏻 for more safetey, use the internal tracks
👉🏻 so modern disks have a copy of unit 0 in the interior unit of the last disk

✔️ Cylinder

if we take the same track in every plate, you have a cylinder
number of cylinder is the same as number of tracks
if you get an error in track 20, linux will say you have an error in cylinder 20
it means the same thing!

✅ Cluster

if you take several consecutive units, you have a cluster
it means minimum size of a file
even if the file is smaller than the size of the cluter, you need to fill it
👀 My picture is 3kb but the cluster size is 4kb.
If I save this picture in the harddisk, this picture file will still occupy 4kb in the harddisk.
not 3kb ❌
and the extra 1kb added to fill the cluster size is called redundance

✔️ Redundance

used for parity, secutiry, protection
used for protection of the file
👀 If the picture is 13kb and cluster size is 4kb, the picture file will occupy 16kb.
File size will be cluster size, or be the multiple of cluster size
the redundance will be 3kb
more redundance ⬆️ more secure the file ⬆️

❓ My video is 21kb, and my cluster is 4kb

- it will occupy 24kb, as it has to be a multiple of 4kb
- and 3kb will be redundance

❓ When you predesign a harddisk, what should I choose? small cluster or big?

small cluster size:
files can be small, will not occupy a lot
👍🏻 you can store many files
👎🏻 but the files will be not very protected, not very safe
🛠️ for normal standard ppl who wants many files in one disk
big cluster size:
file sizes will be big
👎🏻 will not be able to save so many files
👍🏻 files will be very protected, lots of redundance
🛠️ for servers, for companies who need protection
❓ I do not know for what I will use this harddisk
use standard
use default for harddisk
when I do not know the use of my disk

✔️ How to change cluster size

you can choose the cluster size when you format the disk
need to format the disk
make sure to backup the disk
right click(contextual)
click on: format the disk
choose dropdown tamaño de unidades asignacion = cluster size
you can also choose harddisk format(NTFS, exFAT…)here

✔️ DEFRAG tool

Due to clusters and redundancies, your HD will have several many holes
what would happen all the extras are moved to the end of the disk
and create a huge big extra at the end of the disk
you can clean it and use it for extra files
that can free up more space
DEFRAG tool: to collect all the holes and make a big space
it improves the capacity of the disk
you can use DEFRAG tool when your harddisk seems out of space

✔️ Patition

set of many many clusters
even if you continue on the next plate
If we go on with the cluster
we change sides, and to another plate, we create a partition
Partitions are portion of a harddisk
harddisk are connected with SATA

✔️ Partitions have a name

/dev/sdalphabet/number

disk: devices, called /dev/sd/
connected by SATA
- dev: device
- sd: SATA Drive, harddisks are connected to the motherboard using SATA wire
- letter: order of the disk(first/second/third…)
  - A: internal
  - B, C, D: external
so, /dev/sda: first internal secondary memory in my computer
/dev/sdb/: second disk in my computer, could be internal or external
/dev/sbc: third disk in my computer
then a number indicating partition of the disk
/dev/sdb/1: first partition of the second disk
/dev/sba/3: third partition of the first disk
The booting unit does not count as a partition
if there is an error in /dev/sdd3: it means in my computer I have at least three disks, and the third portion is failing.
This does not mean my computer will fail, it just means my fourth fisk, an external disk is failing, but my internal disk is safe

⭐️ Exam Question

A: cylinder, track
B: sector
C: unit, intersector and and track, unit 0 is the most important!
D: cluster
partition: several clusters(not on picture, but partition is several clusters)

✅ Capacity of a disk

Capacity of a disk is total number of sides in a disk
unit is H(header)
If I have 4 plates, I have 8 sides
I have 8 heads
so number of sides = number of heads
Capacity of a disk
multiply number of heads
multiply number of sectors(triangles 🔺)
multiply number of tracks(circles 🔴)
capacity of each unit
👉🏻 Capacity of a disk H * S * T * U

✅ Partition table

If I want to go to the very last partition,
can I jump? YES ⭕️
or do I have to roll down all the partition? NO ❌
In disk, there is an index of partitions
It is called the Partition table
this table is located inside the harddisk
It is also inside the Unit 0 of the harddisk

✔️ What is inside the partition table?

name of the partition /dev/sda1, /dev/sda2
beginning of the partition plate 0, side 0, sector 1, track 10
end of the partition plate 0, side 1, sector 10, track 10

✅ What happens if I break/damange my unit 0?

you lose the index ⭕️
you do not lose the information stored in the HD ❌
Can I still recover the data?
If there is a way of restoring the index, you can restore your disk 👍🏻
If you cannot restore the index, the HD will just be a huge 0s and 1s,
we do not know where things start and end

✅ Type of partition

there are four
and three more optional, more specific types

1️⃣ Primary Partition

store the OS
OS that I want to boot/ use
If there is an OS that you want to use, you need to store it in the primary partition
🆚 If there is an OS that you want to test, save it in the logical patition

2️⃣ Active Partition

chosen OS
partition that you choose to use
the partition that contains the chosen OS
when Jose gives class, he uses windows active partition
when Guadalupe gives class, she uses linux active partition
bc one header can read at once
so only one active partition

3️⃣ Logic Partition

used for (1) storing data
and (2) OS for demo(for testing) mode

4️⃣ Extended Partition

set/group/conjunto of logical partitions
several logical partitions gathered together
used for organizing logical partitions purpose
also called umbrella
like an umbrella that embraces the logic partitions
in a disk, there can be only one extended partition, with several many logical partitions

✔️ Distribution of partition is always symbolized with a formula

number of primary + if use extended + num of logical
2P + E(3L)

In my computer I want...
Windows 10, bootable(useable), kernel of the OS
Ubuntu 24, bootable(kernel)
Mac OS, just for testing
Data of the windows OS separated from the OS system, in a different partition
Data of Ubuntu OS separate from OS

Which type of partition should I give to Windows 10?
- primary partition, I want to use it

Which type of partition should I give to Ubuntu?
- primary partition, bc I want to use it

Which type of partition should I give to Mac OS?
- logic partition, just for testing

Which type of partition should I give to data windows?
- logical partition

Which type of partition should I give to Ubuntu data?
- logical partition
- and create an extended partition for three logic paritions

👉🏻 2P + E(3L)

✔️ Furthermore, there are three special types of partitions

5️⃣ Reserved Partition

partition used for factory settings
when you want to make the computer to factory settings, use this partition
not obligatory ❌
optional ⭕️

6️⃣ Recovery Partition

storing recovery points
like taking snapshots
Recovery point: situation of the computer that you want to remeber
all recovery points are stored in recovery partition
not obligatory ❌
optional ⭕️

7️⃣ Booting Partition

NOT Unit 0 ❌
partition for storing the menu that helps you to choose
which partition who want to activate
Bootstrap loader: the technical name of the menu
so the booting parition saves the bootstrap loader
not obligatory ❌
optional ⭕️

💡 Unallocated space

Final partition that you leave at the end, you leave it for future use
If there is a partition that I do not use the use for
recommended to have it

✅ Format of the partition

which use you are going to give to the partition

format is the same as file system

1️⃣ NTFS

when using partition for windows

2️⃣ ext2, 3, 4

when using partition for Linux

3️⃣ FAT 32

for files less than or equal to 4GB

4️⃣ exFAT

files bigger than 4GB

5️⃣ HFS, Hierarchical FS

Mac, IOS

6️⃣ F2FS

Flash Friendly
Android

👉🏻 When we design a disk, we need to decide type and format of partition

In my computer I want...
Windows 10, bootable(useable), kernel of the OS
Ubuntu 24, bootable(kernel)
Mac OS, just for testing
Data of the windows OS separated from the OS system, in a different partition
Data of Ubuntu OS separate from OS

1.
Which type of partition should I give to Windows 10?
- primary partition, I want to use it
Which format should I give to windows 10?
- NTFS

2.
Which type of partition should I give to Ubuntu?
- primary partition, bc I want to use it
Which format should I give to Ubuntu, which is a type of Linux?
- ext2, 3, 4...

3.
Which type of partition should I give to Mac OS?
- logic partition, just for testing
Which format should I give to Mac OS?
- HFS

4.
Which type of partition should I give to data windows?
- logical partition
Which format should I give to data windows?
- NTFS

5.
Which type of partition should I give to Ubuntu data?
- logical partition
- and create an extended partition for three logic paritions
Which format should I give to Ubuntu data?
- ext2, 3, 4...

👉🏻 2P + E(3L)
👉🏻 When we design a disk, we need to decide type and format of partition

❓ Is it a good idea to have data and OS in different partitions?

If OS and data were in a same partition
and I want to update to Windows 11,
then you lose the data!
👎🏻 If we put kernel and data in the same partition, it is all mixed
if you change the OS, you lose the data
So, we keep them separate
as we can change the system without losing the data

✔️ Version hopping, Distro hopping

Version hopping: putting OS and data separate in Windows
Distro hopping: putting OS and data separate in Linux
change the OS without losing the data

✅ Tunnel/Channel of communication

If I store data in a logical partition in one certain format, like NTFS
that file will not be reachable by the other OS system that has linux
UNLESS you create a common channel/tunnel for the both OS systems
1️⃣ If I want to create a communication channel lin-win for documents of 3GB
logical partition, as it is for data
all logical partitions are inside the umbrella
logical partition out of the umbrella will be dangerous!
umbrella will have to extend to also include this communication channel
format will be FAT32, as common for linux and windows, and less than 4GB
2️⃣ Create another communication channel lin-win for Virtual Machines, that has 30GB
type of partition should be logical, as it is data
virtual machines, even if they contain OS, they are considered data
inside the umbrella
need to extend the umbrella a bit more
format will be exFAT, as it is for both linux, windows
and more than 4GB
👉🏻 together with the previous exmaple, it would be 2P + E(5L)

❓ Can I create a partition without a format?, Unallocated parition

I can create it, but it will not be useable
You can have it for future use
for extra space for future partitions
as we do not know the use yet, we leave it without format
Unallocated parition: partition without format

✔️ Volume

volume: set of partitions with the same format
several partitions with the same format
example: in the example above, there are several NTFS
they all together 1, 4 create a volume NTFS
several ext 2, 5 create volume ext
❓ If I format a volume, is it the same as formatting a partition?
No, if we format partition 3, we are just losing the data
If we format the volume NTFS, we are also losing the OS and the data
also destroy data and kernel
⚠️ If you format the volumne, you will format all the partitions of the same format
❓ If windows OS is formatted, but the logical partition with data is still there,
you can access the data if you pass it through the communication tunnel
and read it

✔️ Tunneling

when we create tunnels for communication among different OS

✅ Let ISO in Nextmode?

Which is the typical situation for systems if we let iso in Next Mode?
If the technician does not control the disk, just let iso do what it wants

✅ How to check my partition in my computer

✔️ In windows

to check how is my partition in my computer
you can see this with command Win+R>diskmgmt.msc
it creates three partitions
(1) one NTFS partition: named letter C
- inside we have booting + kernel + SWAP(helper for RAM, in linux its called Paging file)
- booting not separate ❌
- It is named C because in the first windows, A, B was taken for disket unit
- although now we do not have external diskets, it uses C
(2) reserve partition
- saves factory settings for windows
(3) recovery partition
- saves recovery points

👉🏻 Windows take all the disk for itself, partioning in 3

point 1: one for saving myself, going back to factory setting and recovering myself
point 2: no verison hopping ❌
- but it will let update from Windows 10 to 11, as it makes backup on the internet
- windows 11 makes you be connected to internet while you update to windows 11, and take your data to the cloud, and brings your data back
- so ppl can change their OS without losing the data
point 3: no tunneling ❌
point 4: booting is not in its own parition, it is mixed with other data
If windows its not perfect, it will not boot at all(blue screen)
as in windows, system and booting is mixed, if there is a problem in the system, you cannot even boot
🆚 this is a difference between linux and windows

✔️ In Linux

Linux is very adaptative
But if you let linux do whatever it wants to(Next mode), it will take the whole HD as well
you can see this with command sudo fdisk-l
- fdisk: show format of the disk
- -l: long information, read me all the details
- sudo: super user do, you have to be an administrator permission
linux will create two partitions
(1) partition for booting
- separate partition for booting
- 👍🏻 as linux has boot separate from the system, it can always boot
- it can also boot with errors in the system
- so you can boot, and fix the errors in the system
- 👍🏻 Linux always!!! boot
(2) all the rest

👉🏻 Linux also takes all for itself

point 1: no tunneling ❌
point 2: no partition for data, no distro hopping ❌
If we do not have hopping, we are trapped in the systems, as we do not want to lose the data

✅ Predesign the disk

If the technician designs the copmmuter
do not let iso do whatever it wants, the technician becomes the boss and controls the disk

✔️ Perfect partition with both Windows and Linux

should have 7 partitions
(1) Windows C partition: for windows kernel + windows booting + windows SWAP
(2) Windows D partition: for windows data, NFTS ➡️ version hopping
other five partitions: for linux partitions
they are visible, you can see it exists, but not understandable by windows
(3) Linux root: one partition of the kernel, the OS of Linux, as Linux is a tree
(4) Linux /boot: for booting Linux, it is kept separate so we can boot even with errors in the system. Linux always boots!
(5) Linux /home: partition for data, home for data ➡️ distro hopping
(6) Linux SWAP: if SWAP is mixed in the system, if there is a problem in the system, SWAP will also have problems. Thus, Linux separates SWAP.
(7) Linux /boot/efi: for extras needed in booting if BIOS is UEFI booting
without /boot/efi, you cannot use extras
this partition is created automatically when the booting has UEFI

👍🏻 with this 7 parititions: flexible, adapative, can change system without losing data

version hopping ⭕️: separating data from booting
tunneling ❌ : tunneling is only made when the disk is big
for tunneling, you need more or less 1TB
Only 5% of computers in companies have this structure
Companies are very outdated

✔️ (Review) Two types of BIOS

legacy: very simple basic booting, rest of work is yours, easier
UEFI: controls the systems interactively, more complicated, more extras
booting with UEFI need extras

📌 In SSD

SSD do not have plates
SSD have pages
like a book with pages
SSD has two sides per page
has a grid with transistors that it places it 0 and 1
store data in transistor
cluster in SSD: portion of a page, minimum size of a file
partition: set of clusters in several pages
Unit 0: tiny portion of the first page
Rule of SSD: you cannot start a partition at the end of a page
even if there is space left in the end of the previous page, you have to start in the next page
👎🏻 SSD has two problems:
👎🏻 losing space, so solid states are very fragmented
👎🏻 loss of information bc of loss of elasticity, some day information will be lost
as SSD is fragmented, there are many portions between partitions
that portion between partition does not belong to any partition
those fragments are not protected, as neither Window or Linux will protect it
The zombie cookies love the unprotected proportions
👎🏻 create unsafe space in SSD
💊 we should give to the partition a very specific size
in order to avoid fragments
If cluster size is 4KB, the perfect cluster size would be a multiple of the cluster size and a multiple of the page
calculate the common and non common factors to the maximum power
if cluster size is 4KB, page size is 30KB, partition size should be 60KB

DAW bilingual, Computer System

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