如何用mysqldump進(jìn)行全量和時(shí)間點(diǎn)備份
mysqldump在mysql中用于邏輯備份,雖然速度不快,但非常靈活,有很多功能,靈活使用的化絕對(duì)是利器。
首先思考一個(gè)問題,mysql為什么要備份,主要還是數(shù)據(jù)安全性,比如主庫(kù)掛了,數(shù)據(jù)不小心被刪除了,所以全量備份非常重要。
是從主庫(kù)還是副庫(kù)進(jìn)行全量備份呢?
1:從主庫(kù)
主庫(kù)比較重要,但其實(shí)備份的時(shí)候并不會(huì)影響數(shù)據(jù)庫(kù)
mysqldump --host= --user= --password= --single-transaction --master-data=1 --flush-logs --databases >~/db.log
—single-transaction 參數(shù)能夠報(bào)紙一致性讀,不會(huì)鎖表,也就是備份的時(shí)候不影響數(shù)據(jù)更新。
it dumps the consistent state of the database at the time when START TRANSACTION was issued without blocking any applications.
因?yàn)橐恢滦宰x,能夠保證coordinates點(diǎn)的位置,即使備份時(shí)間很久,也能得出正確的同步位置點(diǎn)。
While a —single-transaction dump is in process, to ensure a valid dump file (correct table contents and binary log coordinates)
—master-data參數(shù)也很重要,導(dǎo)出的語句會(huì)包含CHANGE MASTER TO語句,包括備份語句同步到的二進(jìn)制文件和位置點(diǎn)。
Use this option to dump a master replication server to produce a dump file that can be used to set upanother server as a slave of the master. It causes the dump output to include a CHANGE MASTER TO statement that indicates the binary log coordinates (file name and position) of the dumped server. These are the master server coordinates from which the slave should start replicating after you load the dump file into the slave.
—flush-logs會(huì)強(qiáng)制重新生成一個(gè)新的二進(jìn)制文件,這樣恢復(fù)的時(shí)候會(huì)比較方便。
2:從副庫(kù)
感覺上從副庫(kù)備份更安全。
mysqldump --host=--user= --password= --dump-slave=1 --flush-logs --apply-slave-statements --include-master-host-port --databases >~/db.log;
— dump-slave和—master-data參數(shù)很類似:
This option is similar to —master-data except that it is used to dump a replication slave server to produce a dump file that can be used to set up another server as a slave that has the same master as the dumped server. It causes the dump output to include a CHANGE MASTER TO statement that indicates the binary log coordinates (file name and position) of the dumped slave’s master. These are the master server coordinates from which the slave should start replicating.
記住一點(diǎn)它獲取的是主庫(kù)的bin log coordinates(不是備份庫(kù)的)
—dump-slave causes the coordinates from the master to be used rather than those of the dumped server
dump出來的語句會(huì)包含 — Position to start replication or point-in-time recovery from。
—apply-slave-statements會(huì)讓dump語句中自動(dòng)包含start和stop slave語句。—include-master-host-port包含主庫(kù)的連接信息。
必須記住一點(diǎn),即使有—single-transaction語句,—dump-slave也會(huì)暫停mysql同步,也就是備份庫(kù)的數(shù)據(jù)是落后于主庫(kù)的,所以一般自動(dòng)化腳本在備份的時(shí)候會(huì)先摘除備份庫(kù)。
This option causes mysqldump to stop the slave SQL thread before the dump and restart it again after.
3:如何進(jìn)行時(shí)間點(diǎn)恢復(fù)
沒有實(shí)戰(zhàn)過,首先基于最近的一次全量備份進(jìn)行恢復(fù),然后將后續(xù)的binlog文件導(dǎo)入(如果這些文件還在的話),所以副庫(kù)最好也備份binlog語句。
如果數(shù)據(jù)被誤刪除了,將備份點(diǎn)(—flush-logs發(fā)揮作用了)到今天凌晨的binlog語句導(dǎo)入進(jìn)來,或者找到安全的binlog位置點(diǎn)進(jìn)行恢復(fù)。至于如何跳過“危險(xiǎn)語句”是比較難控制的。
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