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Displaying posts with tag: mysql recover corrupt innodb database (reset)
Recover corrupted or crashed MySQL database online

Earlier before we blogged about ways to recover corrupt MySQL database with TwinDB Data Recovery Toolkit. However learning curve of the toolkit is rather steep. It takes time to get familiar with InnoDB internals and the tool. And let’s be honest nobody gets prepared for data loss – people who prepare for disaster recovery take and verify backups. So when an accident happens precious time has to be spent on learning and scripting.

At TwinDB we automate everything. With data recovery automation is not straightforward, but we did it. In the post I will show how to recover corrupted MySQL database in the fastest possible way.

MySQL Data Recovery Portal

MySQL Data Recovery Portal is a web interface to TwinDB …

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How to evaluate if MySQL table can be recovered

What are odds MySQL table can be recovered?

This is the most asked question. Every single customer asks if their MySQL table can be recovered. Although it’s not possible to answer that with 100% confidence there are ways to estimate recovery chances. I will describe few tricks.

Generally speaking, if data is on media there are high odds TwinDB data recovery toolkit can fetch it. Where to look for depends on accident type.

Online MySQL data recovery toolkit

On our Data Recovery portal you can upload an .ibd file and check if the InnoDB tablespace contains any good records. The table space may be corrupt. The tool should handle that.

DROP TABLE or DATABASE with innodb_file_per_table=OFF

If …

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Recover Corrupt MySQL Database

The unDROP for InnoDB tool can be used to recover corrupt MySQL database. In this post we will show how to repair MySQL database if its files became corrupted and even innodb_force_recovery=6 doesn’t help.

The corruption of InnoDB tablespace may be caused by many reasons. A dying hard drive can write garbage, thus page checksum will be wrong. InnoDB then reports to the error log:

InnoDB: Database page corruption on disk or a failed
InnoDB: file read of page 4.

MySQL is well know for poor start-up script. A simple upgrade procedure may end up with two mysqld processes writing to the same tablespace. That leads to the corruption too. Sometimes power reset corrupts not only InnoDB files, but file system becomes unusable for the operating system.

InnoDB …

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UnDROP tool for InnoDB

While working on data recovery cases I had been maintaining Data Recovery Tool for InnoDB. It proved to be useful in most of disaster scenarios, but still has some limitations:

  • page_parser is slow. It scans a stream of bytes in order to find InnoDB pages. Being single-threaded it couldn’t leverage power of modern multi CPU servers. The same time customer’s databases tend to grow. It’s not uncommon to see over terabyte databases (I recovered once as large as 100 terabytes database!). Taking this into account recovery time quite often was painfully long.
  • You have to recompile constraints_parser for every table. It takes long if there are many tables. To make it worse constraints_parser isn’t very smart about memory allocation, so a binary required about 250MB. Thus, to …
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Showing entries 1 to 4