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NS0-701: Physical and Logical Storage Resources

NS0-701 · Work through your exam, one topic at a time.

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Physical and Logical Storage Resources

What this domain tests

This domain covers how disks become aggregates, how aggregates become volumes and LUNs, and how space is actually consumed.

Core rules

  • Aggregates are built from RAID groups using RAID-DP (double parity) or RAID-TEC (triple parity) and draw from hot spare disks; ONTAP reserves spares and warns when the spare count falls under the low threshold.
  • Advanced Drive Partitioning puts the root partition and a data partition on the same disk pair, so small systems do not waste whole disks on the root aggregate.
  • WAFL writes consistency points and handles Snapshots, deduplication, compression, and compaction; Snapshots consume space from the volume and, once the Snapshot reserve is exhausted, can spill into free space.
  • Volume guarantee can be none (thin, overcommitted) or volume/file (reserved). Autosize can grow or shrink a volume within a maximum.
  • FlexVol is the standard volume; FlexGroup is a scale-out volume with multiple constituents in one namespace; FlexClone is a writable point-in-time copy that shares blocks until changed.

Worked example

Provisioning a 20 TB FlexVol on a 15 TB aggregate succeeds when the guarantee is none, because ONTAP does not reserve the space. Writes later fail with ENOSPC once the aggregate fills. The fix is to check volume show -fields size,available,percent-used,guarantee and either raise the guarantee or move the volume to an aggregate with real free space.

Traps

Treating percent-used as only user data - it includes Snapshot copies. Assuming a FlexClone immediately doubles space usage. Forgetting that aggregate Snapshot reserve and volume Snapshot reserve are separate settings.