You might want to consider using RAID (Redundant Array of Inexpensive Disk) to protect against loss of data, which helps to make your data systems more fault tolerant.
As the name suggests, RAID is based on multiple inexpensive disk drives to create redundancy of data, or a way to recover the data.
The 6 levels of RAID are:
RAID Level 0 — Disk Striping
RAID level 0 provides no data protection. Data is simply striped and split across disks evenly.
If one disk fails, the entire array could fail. RAID 0 is normally used to increase performace, as apposed to single-drive performance.
RAID Level 1 — Disk Mirroring and Duplexing
RAID Level 1 simply copies data in one disk into another.
This configuration requires a minimum of 2 hard disks. The array can only be as big as the smallest member disk.
RAID 1 is particularly useful when read performance is highly desired, and guards against controller failure. There is no parity, striping, or spanning of disk space across multiple disks.
RAID Level 2 — Disk Striping with ECC (Error Correction Code)
In RAID 2, data is striped across several disks with error correction. Error correction allows data to be reconstructed.
The Hamming Code is used for ECC. RAID 2 is not a common practice.
RAID Level 3 — ECC Stored as Parity
Another uncommon configuration, in RAID 3 data is striped across several disk, with a dedicated disk for storing parities.
Parity may be computed at byte-level striping.
RAID Level 4 — Disk Striping with Large Blocks
Like RAID 3, RAID 4 has a dedicated disk for storing parities, except a single parity block is used.
Here’s block-level striping is used, without parity recomputation when the configuration is extended online.
RAID Level 5 — Disk Striping with Parity
In RAID 5, data is written across an array of disks and maintains parity information.
If one disk in an array fails, the system can recover the data from the remaining disk data and parity information.
Read performance is good, but write performance is slower. RAID 5 requires a minium of 3 disks. It allows for a single disk failure before any data is lost.
RAID Level 6 — Disk Striping with Double Distributed Parity
RAID 6 is an extension of RAID 5, using 2 parity blocks and distributed across disks.
RAID 6 offers high fault tolerance, and is used especially in mission-critical systems. It allows for 2 disk failures before any data is lost.
Other factors in setting up a RAID array
Besides costs of hard disk as a factor in building a RAID array, the performance of RAID also varies. Higher RAID levels demand higher computational performance in computing the parity, as well as rebuilding the array on newly replaced diskes on a disk failure event.
It’s common to see rebuild times of RAID 6 to stretch over 24 hours.
The price of RAID controllers varies by its specifications.
Types of Backup
In keeping your data safe, remember these common backup strategies:
- Full copy — cloning files from one disk to another.
- Full backup — copying files marked for backup, from one place to another.
- Incremental backup — updating files that are backup with the changed ones only.
- Daily copy — copying files that have changed on a given day, including files not marked as backed up.
- Differential backup — changed files since last or full incremental backup, onfiles marked as backup
