How does a RAID 4 or RAID 5 volume work?

RAID 4 and RAID 5 are parity-based RAID levels that provide both performance improvement and data protection. They work by distributing your data and calculated parity information across multiple drives, allowing the volume to survive a single drive failure.

How it works

Data distribution: When you write a file to a RAID 4 or RAID 5 volume, SoftRAID splits the data into blocks (called “stripe units”) and writes them across multiple drives simultaneously. Along with your data, SoftRAID calculates and stores “parity” information—a mathematical representation that can be used to reconstruct missing data if a drive fails.

RAID 4 vs RAID 5:

• RAID 4: Stores all parity information on a single dedicated drive. This makes parity calculations faster but can create a bottleneck on the parity drive during write operations.
• RAID 5: Distributes parity information evenly across all drives in the array. This spreads the write load and typically provides better performance than RAID 4.

Drive failure protection: If any single drive fails in your RAID 4 or 5 volume, SoftRAID can use the parity information stored on the remaining drives to reconstruct the missing data on-the-fly. You can continue working with your files while you replace the failed drive. Once a new drive is installed, SoftRAID automatically rebuilds the volume.

Capacity: RAID 4 and RAID 5 volumes use the capacity of one drive for parity storage. For example:

• 4 x 2TB drives = 6TB usable space (one drive’s worth used for parity)
• 6 x 4TB drives = 20TB usable space (one drive’s worth used for parity)

Minimum drives: RAID 4 and RAID 5 require a minimum of 3 drives.

When to use RAID 4 or 5: These RAID levels are ideal when you need both good performance and protection against drive failure, and can afford to dedicate one drive’s capacity to parity storage.

For more information se the article on “Choosing the right RAID level for your needs”.