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RAID 1 vs RAID 5 vs RAID 10 comparison

  • RAID 1 array: Two mirrored disks. The data is identical on both drives. Data block 1 is copied on disk 1 & 2. Data block 2 is copied on disk 2 & 3
  • RAID 5 array: minimum of 3 disks. Data blocks are striped across 3 drives minimum. Data block 1 is copied on disk 1 & 2 and a parity bit on disk 3. Data block 2 is copied on disk 2 & 3 and parity bit on disk 1. Data block 3 is copied on disk 1 & 3 and parity bit on disk 2. Data block 4 is copied on disk 1 & 2 and parity bit on disk 3.
  • RAID 10 array: minimum 4 disks. Data blocks are striped across 2 arrays of 2 mirrored drives. Data block 1 is copied twice on disk 1 & 2. Data block 2 is copied twice on disk 3 & 4. Data block 3 is copied twice on disk 1 & 2. Data block 4 is copied twice on disk 3 & 4

Both RAID 1 and RAID 5 are redundant. If we lose one drive, the RAID array will still work.

RAID Storage capacity loss:

  • RAID 1: We lose 50% of storage capacity since 1 drive is only used as a real time backup
  • RAID 5: We lose 33,33% of storage capacity since data striping occurs over 3 drives
  • RAID 10: We lost 50% of storage capacity since data blocks are striped across 2×2 mirrored disks 

RAID storage performance comparison:

RAID 1 vs 5 vs 10 performance in READ mode:

RAID 5 and RAID 10 are faster than RAID 1. Then RAID 5 is always faster than RAID 10 whatever the mode, random read or continuous read.

RAID 1 vs 5 vs 10 performance in WRITE mode:

RAID 5 is the slowest because parity has to be calculated for every data block. Then, in second position would be RAID 1 because the data blocks should be written on 2 drives. RAID 10 is the fastest because data blocks are striped between two arrays.

Disaster recovery:

  • RAID 1: The user just needs to rebuild the RAID 1 by mirroring the drive and check if the bootloader is ok.
  • RAID 5: When a disaster happens, the array slows down to recover the missing data block thanks to the parity check. Someone has to replace the faulty drive, rebuild the array and regenerate the boot.
  • RAID 10: A new drive should be added to the array that has no mirrored drive. The user should check if the bootloader is ok on the new drive.

Conclusion:

  • RAID 1: Best for smallest power consumption (2 drives) and redundancy. RAID 1 is definitely greedy in terms of storage capacity.
  • RAID 5: Best for many fast reads. Good balance in terms of power consumption (3 drives). Also, RAID 5 is the least greedy solution in terms of storage capacity.
  • RAID 10: Best for many fast writes. Cookie monster in terms of power consumption (4 drives). It is the solution that requires the maximum number of drives.

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