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Veritas Quick I/O and Cached Quick I/O

原创 Linux操作系统 作者:BTxigua 时间:2009-03-19 12:32:40 0 删除 编辑

1、什么是Quick I/O and Cached Quick I/O?

VERITAS Quick I/O is a special feature of the VERITAS File System (VxFS) for the VERITAS Database
Edition for Oracle.  The Database Edition is an integrated suite of system software enhancements and
configuration guidelines that combine to help system administrators and database administors configure
Oracle database servers.

VERITAS Quick I/O provides a raw device interface to regular files created under VxFS.  It bypasses
certain file system overhead operations (i.e. locking layer) and supports kernel asynchronous I/O (KAIO),
hence Quick I/O provides the benefits of both file system manageability and raw device performance.
Cached Quick I/O is an enhancement to Quick I/O that enables Oracle DBAs to utilize their large system
memories more effectively.

传统的文件系统,由于对文件的single write lock存在,导致文件系统在并发环境中读写效率比较低。而裸设备则不存在这个问题。Quick I/O其实就是消除了单写锁,提高文件系统的效率。

Cached Quick I/O是对Quick I/O的一种增强处理,核心的思想就是不断的记录访问的文件的频度,将最热的文件放在cache中,提高cache的命中率,从而提高文件系统的效率。

可以简单的理解这两个特性:

1)Quick I/O解决的是传统的unix文件系统的single write lock问题。

2)Cached Quick I/O解决的是cache的命中率问题。

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