Huawei OceanStor distributed storage supports multi-level cache technology. During the cache read process, which of the following is the priority for read hits?

Question

Options

• ASSD Read Cache
• BSSD Write Cache
• CMemory Read Cache
• DMemory Write Cache

• A
  3% (2)
• B
  10% (7)
• C
  6% (4)
• D
  82% (58)

Explanation

In Huawei OceanStor's multi-level cache hierarchy, Memory Write Cache has the highest read hit priority because data written there represents the most recent version - serving reads from it first is essential for data consistency. If a read request hits data that was recently written but not yet flushed to persistent storage, returning anything other than the write cache copy would yield stale data, which is a correctness violation.

Memory Read Cache (C) is wrong because, while also in memory, it holds previously read (not written) data and is checked after the write cache - the write cache must take precedence to guarantee up-to-date reads. SSD Write Cache (B) is wrong because SSD is slower than memory; the system checks all memory-tier caches before falling to SSD-tier caches. SSD Read Cache (A) is wrong for the same reason and also because it's the last resort - only a miss at all higher levels sends the read to SSD cache or underlying storage.

Memory tip: Think of the priority as "newest first, fastest first" - write caches hold newer data than read caches, and memory is faster than SSD, so the order is: Memory Write → Memory Read → SSD Write → SSD Read.

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