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RAID1 replace broken HDD

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If you see something like this on your monitor or in your logs, you should worry about your important data.

And immediately change your HDD!

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ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
ata1.00: failed command: FLUSH CACHE EXT
ata1.00: cmd ea/00:00:00:00:00/00:00:00:00:00/a0 tag 0
res 40/00:0c:b9:68:55/00:00:05:00:00/40 Emask 0x4 (timeout)
ata1.00: status: { DRDY }
ata1: hard resetting link
ata1: link is slow to respond, please be patient (ready=0)
ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata1.00: configured for UDMA/133
ata1: EH complete

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RAID 6

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A RAID 6 is another form of parity protection for disks. Called dual parity too.

Requirements: 4 Disks
Capacity: (Size of Smallest Drive) * (Number of Drives – 2)
Read: Very good read performance
Write: Poor write performance due to dual parity overhead and complexity

For this RAID level you should use a hardware controller.

RAID 5

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A RAID 5 uses block-level striping with parity data distributed across all member disks.

Requirements: At least 3 drives
Fault Tolerance: (N – 1) Can tolerate loss of one drive
Capacity: (Size of Smallest Drive) * (Number of Drives – 1)

RAID 1

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RAID 1 – Mirroring without parity or striping.

– Minimum disks: 2
– Data redundancy (mirror)
– One disk may fail
– Effective protection against physical disk failure

RAID 0

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RAID 0 is a simply data stripe over several disks.

– No data protection
– Better performance
– Requirements: At least 2 drives
– Put several disks to one bigger one
– If one disk fails, you lose all your data
– Raid 0 is excellent for non-mission critical situations