3.8 Partitions

✅ 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 0

• intersection of sector 0 and circle 0
• unit 0 stores the booting system
• 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

✔️ 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

• 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

• 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. This picture file will still occupy 4kb in the harddisk.
• and the extra 1kb added to fill the cluster size is called redundance

✔️ Redundance

• used for parity
• 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 ⬆️

✔️ 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

• 👉🏻 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, default for harddisk

✔️ How to change cluster size

• need to format the disk
• make sure to backup the disk
• right click(contextual)
• format the disk
• choose 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

• If we go on with the cluster

• we change sides, and to another plate, we create a partition

• partitions have a name
• disk: devices, called /dev/sd/
• connected by SATA
  • dev: device
  • sd: SATA
  • letter: order of the disk(first/second/third…)
    • A: internal
    • B, C, D: external
  • then a number indicating partition of the disk
• so, /dev/sd/A/1, /dev/sd/B/1

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• 1️⃣
• 2️⃣
• 3️⃣
• 4️⃣ 👍🏻 👎🏻

⭐️⭐️⭐️ EXAM ⭐️⭐️⭐️
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