Last, it is not yet possible to backup single InnoDB tables by copying the. You can just look up the top 10 largest files under your MySQL data directory (and subdirectories), and monitor their size. You don’t need access to MySQL, to use SHOW TABLE STATUS or to query the INFORMATION_SCHEMA. One other nice thing about innodb_file_per_table is that it is possible to monitor table size on the file system level. With the new InnoDB plugin, disk space is also regained when execuing a TRUNCATE TABLE log statement.įragmentation is not as bad as in a single tablespace: the data is limited within the boundaries of a smaller file. But still – it allows us to regain disk space. Sure, this takes a long time, during which the table is completely locked: no writes and no reads allowed. Once comlete, the original table is removed, and the new table renamed as the original table. Only existing data is added to the new table. What will happen is that a new, temporary file is created, into which the table is rebuilt. In our log table example, we purge many rows (up to 90GB of data is removed). The last two seem conflicting, don’t they? Let’s explain. It is possible to regain space per tablespace. Tablespace is not shared among different tables, and certainly not among different schemes.Įach file is considered a tablespace of its own. Or you can utilize mk-parallel-dump to speed things up (depending on your dump method and accessibility needs, mind the locking). Assuming you’re only using InnoDB, a dump with –single-transaction will do the job. Mysqldump would be your best choice if you only had the original machine to work with.
If it was 120GB, of which only 30GB are used, you still get a 120GB backed up and restored. The funny thing is, the ibbackup utility will copy the tablespace file as it is. The best way to solve this is to setup a new slave (after purging of the rows), and dump the data into that slave. It means the disk needle needs to move large distances. But having a file which consumes some 80-90% of disk space is a performance catastrophe. Sure, the space would be reused by InnoDB. I’ve seen more than once how certain tables are left unwatched, growing until disk space reaches 90% and SMS notifications start beeping all around. It does not release storage to the file system. So after purging those rows from the log table, the tablespace file (usually ibdata1) still keeps the same storage.
This same nice property also translates to a not so nice one: data can be greatly fragmented across the tablespace.Īn annoying property of InnoDB’s tablespaces is that they never shrink.
Thus, if I purge many rows from my log table, the now unused space can be occupied by new rows of any other table.
#Trim enabler volume not writable or low on space free#
This allows for the following nice property: free space can be shared between different tables and different schemes. Having everything in one big file means all tables and indexes, from all schemes, are ‘mixed’ together in that file. I will discuss the advantages and disadvantages of the two options, and will strive to convince that innodb_file_per_table is preferable. Throw everything in one big file (optionally split). When working with InnoDB, you have two ways for managing the tablespace storage: Here is a nice article by Shlomi Noach, where I found (this and more information about) this.Ĭredits to Shlomi Noach. The shortest way I found was: ALTER TABLE YOURTABLE ENGINE=InnoDBĪfter truncating or deleting the unvanted records I ran this and the tablespace shrinked.
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