昨天由于机房掉电自己的mysql数据库中大量表都出现了无法访问或正使用的情况,后来查了可以使用mysql myisamchk命令进行修复,下面我来介绍一下.
Posted on December 31, 2009 by axl MyISAM是MySQL的预设storage engine. MyISAM table很容易烂掉(corrupted)。
此文章将教你如何检查/修复这些烂掉的MyISAM tables.
每次你在MySQL DB 制造一个 table,将会在档案系统上同时制造出*.frm、*.MYD，跟*.MYI等三种格式的档案.
*.frm = 用来储存资料表格式(file to store table format)
*.MYD(MyData) = 用来储存资料(file to store data)
*.MYI(MyIndex) =用来储存索引(file to store index)
如何检查DB?哪个table 需要修复,用root 执行以下指令,假设要检查DB1下的各个table,代码如下:
#myisamchk /var/lib/mysql/DB1/*.MYI >> /tmp/myisamchk.log
萤幕输出中,如果发现以下字样,该资料表就应修复.
- myisamchk: error: Keypointers and record positions doesn’t match
- MyISAM-table ‘/var/lib/mysql/DB1/news_post_comment.MYI’ is corrupted
- Fix it using switch “-r” or “-o”
- myisamchk: warning: 1 client is using or hasn’t closed the table properly
- MyISAM-table ‘/var/lib/mysql/DB1/news_post.MYI’ is usable but should be fixed
- myisamchk: warning: 1 client is using or hasn’t closed the table properly
- MyISAM-table ‘/var/lib/mysql/DB1/news_post_push_log.MYI’ is usable but should be fixed
Redirect出来的档案中会显示更多资讯,代码如下:
- Checking MyISAM file: /var/lib/mysql/DB1/yam_bbauth.MYI
- Data records: 14 Deleted blocks: 0
- - check file-size
- - check record delete-chain
- - check key delete-chain
- - check index reference
- - check data record references index: 1
- - check record links
如何利用myisamchk修复烂掉的tables,找出烂掉的table之后,用以下指令修复,代码如下:
- #myisamchk –r /var/lib/mysql/DB1/news_post_comment.MYI
- - recovering (with sort) MyISAM-table ‘/var/lib/mysql/DB1/news_post_comment.MYI
- Data records: 1
- - Fixing index 1
如果table正被某个application使用,你可能会看到,clients are using or haven’t closed the table properly.
所以建议修复前将mysqld关掉或用FLUSH TABLES锁住TABLES,防止修复时有application对DB TABLE做更动.
如何让检查跟修复同时进行,代码如下:
- #myisamchk
- myisamchk: MyISAM file /var/lib/mysql/DB1/groups.MYI
- myisamchk: warning: 1 client is using or hasn’t closed the table properly
- myisamchk: MyISAM file /var/lib/mysql/DB1/profiles.MYI
- myisamchk: warning: 1 client is using or hasn’t closed the table properly
-
- • s, –silent option: Prints only errors. You can use two -s to make myisamchk very silent.
- • -f, –force option: Restart myisamchk automatically with repair option -r, if there are any errors in the table.
- • -F, –fast option: Check only tables that haven’t been closed properly.
- • -U –update-state option: Marks tables as crashed, when it finds any error.
修复时手动分配记忆体给庞大的DB,庞大的table,修复需要很长的时间,修复时可以手动增加记忆体参数,代码如下:
- # myisamchk
- -read_buffer_size=4M
用myisamchk 获取table资讯,代码如下:
- #myisamchk -dvv profiles.MYI
- MyISAM file: profiles.MYI
- Record format: Packed
- Character set: latin1_swedish_ci (8)
- File-version: 1
- Creation time: 2007-08-16 18:46:59
- Status: open,changed,analyzed,optimized keys,sorted index pages
- Auto increment key: 1 Last value: 88
- Data records: 88 Deleted blocks: 0
- Datafile parts: 118 Deleted data: 0
- Datafile pointer (bytes): 4 Keyfile pointer (bytes): 4
- Datafile length: 6292 Keyfile length: 6144
- Max datafile length: 4294967294 Max keyfile length: 4398046510079
- Recordlength: 2124
- table description:
- Key Start Len Index Type Rec/key Root Blocksize
- 1 2 3 unique int24 1 1024 1024
- 2 5 765 unique char packed stripped 1 2048 4096
- Field Start Length Nullpos Nullbit Type
- 1 1 1
- 2 2 3 no zeros
- 3 5 765 no endspace
最后一招:#myisamchk --help,MySQL 使用 myisamchk 修复 *.MYI 时,出现下述讯息:
- myisamchk: Disk is full writing '/tmp/ST3lJjsW' (Errcode: 28). Waiting for someone to free space... (Expect up to 60 secs delay for server to c ontinue after freeing disk space)
- myisamchk: Retry in 60 secs. Message reprinted in 600 secs
解法1:
■由讯息可以知道, myisamchk 需要使用到 /tmp,/tmp 容量不够就会出现此讯息,所以如果 /tmp 可以清出空间,清出 /tmp 的空间就可以解决了,但是如果 /tmp 本身切的就不够大,可以使用下述解法.
解法2:此解法取自: free disk space error using myisamchk
■myisamchk -rq --sort_buffer_size=256M --key_buffer_size=256M --read_buffer_size=32M --write_buffer_size=32M --sort-index --analyze --tmpdir=/more-disk-space-directory/ /var/lib/mysql/database/T1.MYI
■?: 修改 --tmpdir=/more-disk-space-directory/ 指定到空间比较大的地方去即可. |
