RAID 1 with two 4 TB drives: simple mirroring, real redundancy, and read-speed gains
RAID 1 with two 4 TB drives mirrors all data identically across both disks, giving you 4 TB of usable capacity from 8 TB of raw storage. This is the simplest form of redundancy: if one drive fails, the other keeps running with zero data loss and zero downtime. You replace the failed drive, the array rebuilds, and you never lose access to your files.
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RAID Calculator
Calculate usable capacity, fault tolerance, and read/write scaling for different RAID levels.
Configuration
Storage Efficiency
Survives 1 drive failure
How this is calculated
RAID 1 costs you 50% of your raw capacity but gives you the strongest single-drive fault tolerance of any RAID level. Read performance improves because the controller can read from both drives simultaneously (theoretically 2× read speed). Write performance stays at single-drive speed because every write must go to both disks. For home NAS users storing family photos and documents, a pair of 4 TB drives in RAID 1 is often the right answer: simple, fast to rebuild, and universally supported by every motherboard, NAS, and RAID card made in the last 20 years.
Verdict
RAID 1 is the safe, simple default for two-drive setups where data integrity matters more than capacity. 50% overhead stings at higher drive counts, but for a basic home NAS or a workstation boot drive, it gives peace of mind without complexity.
Frequently asked questions
Does RAID 1 protect against file corruption or ransomware?
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