December 2012
Intermediate to advanced
572 pages
13h 8m
Chinese
Content preview from HBASE技術手冊
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第八章
架構
對於進階使用者（或那些就是愛冒險的人）而言，完整地瞭解其所選擇系統背後是如何
的工作，這會非常有用。本章會解釋 HBase 的各個運作單元，以及它們相互之間是如何
運作。
搜尋 VS. 傳遞
然而，在研究架構本身之前，我們首先針對一般關聯式資料庫管理系統（RDBMS）及
非傳統儲存架構之間的根本不同點來做探討。特別的是，我們將簡要地介紹 B-trees 或
者更確切地說是
B+ trees
1
，它們通常被使用在關聯式儲存引擎，以及
日誌式結構合併
樹
2
，這在某些程度上形成了 Bigtable 的儲存架構基礎，如在第 16 頁“組件”中所談
到的。
請注意，關聯式資料庫管理系統並不是只採用 B-tree 結構，也不是所有的
NoSQL 解決方案都使用不同的架構。你會發現一個各式各樣的混搭型技術，
但都有一個共同的目標：它們會針對手頭上的問題，使用最佳策略解法。
B+ Trees
B+ tree 有一些特有的特色，它允許高效率的插入、尋查（lookup）和刪除由鍵值所識別
的記錄。就每一個 segment（也稱為
page
）的 key 數量而言，它們呈現一個動態、具有
上下界的多層級索引結構。使用 segment，達到了比二元樹更高的扇出（fanout），這大
大降低了查找某個特定的 key 所需的 IO 操作數。
1 參考維基百科上的“B+ trees”介紹
(
http://en.wikipedia.org/wiki/B%2B_tree
)
。
2 參考 O
’
Neil et al., 1996 的“LSM-Tree ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.