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Re: Doublewrite block number in XtraDB



Thank you for letting me know about the innodb_doublewrite_file parameter.
I understand that it existed in Percona XtraDB for MySQL 5.5 but was not
ported to their MySQL 5.6 based XtraDB. The MariaDB documentation at
https://mariadb.com/kb/en/mariadb/xtradbinnodb-doublewrite-buffer/ agrees
that the option existed before MariaDB Server 10.0 (which is based on MySQL
I think that this would be a rather straightforward change from the design
point of view. On startup, InnoDB would look for both the doublewrite files
(I would consider using one file for each physical page size) and the
built-in doublewrite buffer. During operation, InnoDB would only write to
the doublewrite files, never to the built-in buffer. I would make the
doublewrite file names hard-coded in the datadir root. I do not see any
reason to make them configurable. If someone wants the files to be written
to a different file system, he could manually create the files elsewhere
and let symbolic links point to them from the datadir.