In Huawei RAID 2.0+, Extent is the smallest unit for hotspot data statistics and migration.

Question

Options

• ATrue
• BFalse

• A
  76% (32)
• B
  24% (10)

Explanation

Answer: A - True

Why the Statement is True

In Huawei RAID 2.0+, the architecture introduces two primary storage units that are important to distinguish:

Chunk: The basic physical storage unit on a disk, typically 64KB in size. Chunks are the foundation of how data is physically laid out across drives in a disk domain. They represent the raw building blocks of the storage pool.

Extent: A logical unit composed of multiple chunks. Extents are typically several megabytes in size (such as 4MB or 64MB, depending on configuration). Crucially, the Extent -- not the Chunk -- serves as the smallest unit for two related functions:

1. Hotspot statistics: The system tracks I/O frequency and access patterns at the Extent level. Each Extent accumulates an access count that identifies it as hot, warm, or cold data.

2. Data migration: When SmartTier (automated storage tiering) moves data between performance tiers (such as SSD, SAS, and NL-SAS), it does so at the Extent granularity. A whole Extent is promoted or demoted as a unit, not individual Chunks.

This design is intentional. Using Chunks (64KB) for migration would generate enormous overhead -- too many small moves. Using Extents provides a practical balance between migration precision and system performance.

Memory Tip

Think of it this way: Chunks are for building storage, Extents are for managing storage. The Chunk is the brick; the Extent is the room. You reorganize rooms, not individual bricks. Hotspot migration works at the room level -- the Extent.

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