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ibdata grows exponentially when file-per-table is configured using InnoDB



Have you ever heard of this?  I am working with a client that has some crazy growth in their ibdata files, even though they have configured file-per-table option.  They are using a Percona patch, and my gut is telling me that something is off on the binaries that they are using from Percona.  Let me know if you ever heard of this.





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Hi Thomas,

I haven't used the Percona patches, but I have seen similar issues with the stock InnoDB. The UNDO log entries can get written to the ibdata file(s), even though you may be using innodb_file_per_table. It is possible that there are large transactions that create lots of undo log entries. It is also possible that the purge thread is not cleaning them up in a timely fashion.
I hear you, and I am actually reading this is normal. I think what is going on is that my client is using a very large innodb log file size (2 GB), and once it flushes, it flushes in a big way. I also read that InnoDB still uses the ibdata files for shared tablespace and internal data dictionary.

Thanks for the quick response . . .
To clarify the impact of the patches: there are two Percona patches which apply here - but both are disabled by default.

One is to increase the number of undo slots so that you can have more concurrent transactions:

(If previously you didn't have the same level of concurrency, then it's completely conceivable with a patched version you can 'bloat' in shared tablespace size).

The second patch is to increase the number of rollback segments (to reduce mutex contention). I don't know whether this would incur any additional space overhead:

Just wanted to post a small follow-up.

When my client originally reported the issue, they were using one ibdata file, and files-per-table was enabled. Their log was growing at 3 GB per day. The fix that I came up with was to use 3 (2GB) ibdata files, and the client decided to change their InnoDB isolation level. The last I heard, their space did not grow past the 3 2GB ibdata files.

Thanks for all the other info . . . will keep on file.



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