RAID

content/2.general/4.raid.md

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+---
+navigation: true
+title: RAID
+main:
+  fluid: false
+---
+:ellipsis{left=0px width=40rem top=10rem blur=140px}
+# RAID
+
+_Redundant Array of Independent Disks_
+
+In computing, RAID (Redundant Array of Independent Disks) is a system that allows multiple hard drives to be combined to improve performance and/or reliability. It works by restructuring and distributing data blocks across the drives.
+
+Originally, RAID systems were hardware-based, meaning a dedicated controller (a specific chip) managed data distribution and RAID operations. Today, most RAID systems (or their equivalents) are software-based. In fact, many software technologies can create RAID-like systems with features not available in hardware RAID, such as automatic repair (data scrubbing), snapshots, and more.
+
+## Different Types of RAID
+
+There are several types of RAID, each offering its own pros and cons. In general, RAID impacts the following five factors:
+
+- Number of drives
+- Total storage capacity
+- Read speed
+- Write speed
+- Fault tolerance (resistance to hardware failure)
+
+::alert{type="warning"}
+:::list{type="warning"}
+  - RAID is not a backup system but a service continuity system! It only allows hot-swapping of drives without interrupting your server or restoring from backup. You still need an external backup system.
+::
+
+### No RAID
+---
+
+<div style="display: flex; align-items: center;">
+  <img src="/img/global/no-raid.svg" alt="Image" style="max-width: 30%; max-height:230px; margin-right: 20px;">
+  <ul>
+    <li>Just your disks, without RAID. Data is stored disk by disk.</li>
+    <li>If you lose a disk, only its data is lost.</li>
+    <li>Total capacity is the sum of all disks.</li>
+</div>
+
+Use your disks without RAID when you're not afraid of data loss and can tolerate service interruptions between failure and backup restoration.
+
+### RAID 0
+---
+
+<div style="display: flex; align-items: center;">
+  <img src="/img/global/raid0.svg" alt="Image" style="max-width: 30%; max-height:230px; margin-right: 20px;">
+  <ul>
+    <li>OS sees 1 drive.</li>
+    <li>Data is striped across all disks.</li>
+    <li>If you lose one disk, you lose all data.</li>
+    <li>High read and write performance (multiplied by number of disks).</li>
+    <li>Total capacity is the sum of all disks.</li>
+    <li>Minimum of 2 disks required.</li>
+</div>
+
+Use RAID 0 when you prioritize performance and are not concerned about data loss. Ideal for temporary, high-speed storage (video editing, AI workloads, etc). Not suitable for long-term storage, as one failure means total data loss.
+
+### RAID 1
+---
+
+<div style="display: flex; align-items: center;">
+  <img src="/img/global/raid1.svg" alt="Image" style="max-width: 30%; max-height:230px; margin-right: 20px;">
+  <ul>
+    <li>OS sees 1 drive.</li>
+    <li>All disks contain identical data.</li>
+    <li>You can lose all but one disk.</li>
+    <li>Improved read speed (scales with number of disks).</li>
+    <li>Total capacity is equal to one disk (e.g., 2×10TB = 10TB).</li>
+    <li>Minimum of 2 disks required.</li>
+</div>
+
+Use RAID 1 for strong redundancy. Each disk contains all data, so performance remains unaffected during a failure. Once failed disks are replaced, data is quickly restored. However, usable storage is limited to one disk’s capacity, making it an expensive solution.
+
+::alert{type="success"}
+:::list{type="success"}
+- __Tip:__ You can combine RAID 1 with other RAID types to create mirrored arrays.
+:::
+::
+
+### RAID 5
+---
+<p align="center">
+  <img src="/img/global/raid5.svg" alt="Image" style="max-width: 40%; margin-right: 20px;">
+</p>
+
+- OS sees 1 drive.
+- Data is striped with parity blocks for redundancy.
+- You can lose 1 disk and recover data.
+- Improved read speed (scales with number of disks).
+- Total capacity is the sum of all disks minus one (e.g., 3×10TB = 20TB).
+- Minimum of 3 disks (4 recommended to reduce capacity loss).
+
+Use RAID 5 when you want reliable storage with 3 to 5 disks and minimal space loss. It tolerates one disk failure but may have degraded performance during recovery, which can take days.
+
+### RAID 6
+---
+<p align="center">
+  <img src="/img/global/raid6.svg" alt="Image" style="max-width: 50%; margin-right: 20px;">
+</p>
+
+- OS sees 1 drive.
+- Data is striped with dual parity blocks.
+- You can lose 2 disks and still recover data.
+- Improved read speed (scales with number of disks).
+- Total capacity is the sum of all disks minus two (e.g., 4×10TB = 20TB).
+- Minimum of 4 disks (6 recommended to minimize space loss).
+
+Use RAID 6 in similar situations as RAID 5, especially with 6 or more disks. More disks mean higher failure risk. RAID 6 offers peace of mind by tolerating two simultaneous failures.
+
+## Software RAID
+(coming soon)