Default RAID policies for local tiers (aggregates)
Either RAID-DP or RAID-TEC is the default RAID policy for all new local tiers (aggregates). The RAID policy determines the parity protection you have in the event of a disk failure.
RAID-DP provides double-parity protection in the event of a single or double disk failure. RAID-DP is the default RAID policy for the following local tier (aggregate) types:
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All Flash local tiers
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Flash Pool local tiers
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Performance hard disk drive (HDD) local tiers
RAID-TEC is supported on all disk types and all platforms, including AFF. Local tiers that contain larger disks have a higher possibility of concurrent disk failures. RAID-TEC helps to mitigate this risk by providing triple-parity protection so that your data can survive up to three simultaneous disk failures. RAID-TEC is the default RAID policy for capacity HDD local tiers with disks that are 6 TB or larger.
Each RAID policy type requires a minimum number of disks:
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RAID-DP: minimum of 5 disks
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RAID-TEC: minimum of 7 disks