Storage and Aggregate Management
This domain tests how physical disks become RAID groups and aggregates, and how capacity and sparing decisions affect availability.
RAID and aggregate rules
Aggregates are RAID containers owned by one node and cannot span nodes. RAID-DP uses two parity disks and tolerates two simultaneous failures; RAID-TEC uses three parity disks and is recommended for very large drives where rebuild times are long. A RAID group has a maximum data-disk count, so large aggregates contain multiple RAID groups. Hot spares must be available for reconstruction, and ADP partitions disks into root, data, and spare partitions so small drive counts remain practical.
Capacity planning
Usable capacity is raw capacity minus parity, WAFL reserve, and aggregate snapshot reserve. Adding disks expands a RAID group or creates a new one; aggregate relocation moves an aggregate between HA partners without data copy. Check state with storage aggregate show and disk ownership with storage disk show -ownership.
Worked example
An aggregate uses 20 x 4 TB disks in one RAID-DP group. Two disks are parity, leaving 18 data disks: 18 x 4 TB = 72 TB raw data capacity. WAFL reserve and aggregate snapshot reserve reduce usable capacity below 72 TB, so a 70 TB provisioning request would be unsafe. Provisioning should also leave room for snapshot growth and rebuild.
Traps
Using RAID-DP with very large drives when RAID-TEC is appropriate; forgetting spare requirements; mixing disk sizes or speeds without checking performance impact; and treating raw aggregate capacity as fully provisionable.