What is RAID?
RAID combines several disks into one so data survives a disk failure or is read and written faster.
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RAID (Redundant Array of Independent Disks) groups physical disks into a single logical drive. The common levels tell you the trade off: RAID 0 stripes data across disks for speed but loses everything if one dies; RAID 1 mirrors two disks so either can fail; RAID 5 and 6 spread parity so one or two disks can fail; RAID 10 mirrors and stripes. Think of photocopies of important papers kept in separate drawers.
Servers, NAS boxes and storage appliances all use it, through a hardware controller or software such as Linux mdadm or ZFS. RAID protects against hardware failure only. It does nothing against deleted files, ransomware or a fire, so the saying goes: RAID is not a backup.
Check before you run this
- Runs with administrator rights. Make sure you understand every line.
cat /proc/mdstat
sudo mdadm --detail /dev/md0
zpool statusSee also: What is a backup snapshot? and What is a cluster?
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See also
- 0102 Proxmox VE storage types: local, LVM-thin, ZFS, NFS and Ceph Proxmox VE stores disks, ISOs, templates and backups in storage pools defined in /etc/pve/storage.cfg. Learn the main storage types, what local and… Intermediate · Explains an idea · Linux Article Disks, LVM & filesystems · Storage 15 Oct 2026
- 0168 Server health check script: disk, memory and failed units A dependency-free bash script that checks disk and inode usage, available memory, load, failed systemd units and pending reboots, and exits non-zero… Intermediate · Cheat sheet · Linux Script Disks, LVM & filesystems · Services & systemd 15 Oct 2026
- 0169 Add a new disk: partition, format and mount it by UUID Find a new disk with lsblk, partition it with parted, create an ext4 or XFS filesystem and mount it permanently through /etc/fstab… Intermediate · Step by step · Linux Article Disks, LVM & filesystems 15 Oct 2026
- 0170 LVM explained: physical volumes, volume groups and logical volumes LVM puts a flexible layer between disks and filesystems, so you can grow volumes, add disks and take snapshots without repartitioning. Intermediate · Explains an idea · Linux Article Disks, LVM & filesystems 15 Oct 2026
- 0171 Extend an LVM logical volume and filesystem online (safe script) A bash script that grows the LVM volume behind a mount point, checks the filesystem type and free space first, and runs… Advanced · Step by step · Linux Script Disks, LVM & filesystems 15 Oct 2026
- 0172 Fix: No space left on device Writes fail because a filesystem is full, out of inodes, or holding space for deleted files that are still open. Find which… Beginner · Fixes an error · Linux Article Disks, LVM & filesystems 15 Oct 2026
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