tailieunhanh - o reilly Unix Backup and Recovery phần 4

Tôi cố gắng để giải thích những điều không được đề cập trong tài liệu hướng dẫn và có thể giải quyết một số đối tượng thẳng thắn hơn so với một hướng dẫn sử dụng được cung cấp bởi nhà cung cấp có thể. Chào mừng bạn đến với thế giới của sao lưu. trang 67 | Volume Verification Another often-ignored area of backup and recovery software is its ability to verify its own backups. There are plenty of horror stories out there about people who did backups for years or months assuming that they were working just fine. Then when they went to read the backup volumes the backup software told them that it couldn t read them. The only way to ensure that this never happens to you is to run regular verification tests against your media. There are several different types of verification Reading part of volume and comparing it There is at least one major vendor that works this way. If you turn on media verification it forwards to the end of the volume and read a file or two. It compares those files against what it believes should be there. This is obviously the lowest level of verification. Page 229 Comparing table of contents to index This is a step up from the first type of verification. This is the equivalent of doing a tar tvf. It does not verify the contents of the file it verifies only that the backup software can read the header of the file. Comparing contents of backup against contents of filesystem This type of verification is common in low-end PC backup software. Basically the backup software looks at its backup of a particular filesystem then compares its contents against the actual contents of the filesystem. Some software packages that do this will automatically back up any files that are different than what s on the backup or that do not exist on the backup. This type of verification is very difficult since most systems are changing constantly. Comparing checksum to index Some backup software products record a checksum for each file that they back up. They then are able to read the backup volume and compare the checksum of the file on the volume with the checksum that is recorded in the index for that file. This makes sure that the file on the backup volume will be readable when the time comes. Verify Verify Verify We .