====== S3 Glacier ======

**What it is:** Low-cost archival storage classes for S3.

**What it’s for:**
  * Long-term retention where retrieval can take minutes to hours.

**Key ideas:**
  * Glacier is used via S3 storage classes (Glacier / Deep Archive).
  * Best paired with lifecycle rules.

**Exam cues:**
  * “archive for years, cheapest, slow retrieval OK” → Glacier Deep Archive.

**Hard words:**
  * *archive* /ˈɑːrkaɪv/: lưu trữ lâu dài
  * *retention* /rɪˈtenʃn/: lưu giữ
  * *retrieval time* /rɪˈtriːvəl taɪm/: thời gian lấy dữ liệu