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[DEMO] RAID basics
Which RAID level to choose and how to check a Linux software RAID.
Applies toDedicated servers
RAID levels
| Level | Minimum disks | Survives | Usable capacity |
|---|---|---|---|
| RAID 0 | 2 | Nothing | Sum of all disks |
| RAID 1 | 2 | All disks but one | One disk |
| RAID 5 | 3 | 1 disk | (n − 1) disks |
| RAID 10 | 4 | 1 disk per pair | Half |
Check a software RAID (mdadm)
bash
cat /proc/mdstat
mdadm --detail /dev/md0In /proc/mdstat, [UU] means both disks are fine. [U_] means a disk failed or dropped out of the array.
Hardware or software RAID?
With hardware RAID, check the status with the controller tool or from IPMI. With software RAID (mdadm), from Linux itself as shown above.