Comments on: Beware: key_buffer_size larger than 4G does not work

By: mysql-d

mysql-d — Thu, 26 Feb 2009 10:29:16 +0000

I think the issues is not with mysql but the file system that is been provided by the operating system.

The EXT 2 file system just provides with 4 Gigs of max file size support. I think you should try with the EXT 3 file system
which is more thatn lots and lots of terabites

Thanks

By: Przemek

Przemek — Mon, 22 Sep 2008 10:11:55 +0000

As of MySQL 5.0.52, values larger than 4GB are allowed for 64-bit platforms (except 64-bit Windows).

By: David W. Juntgen

David W. Juntgen — Thu, 26 Apr 2007 04:58:51 +0000

Currently all version of MySQL have a limit to the max size of the key_buffer_size, which is set to 4G.

http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html

But…there are ways around this limitation, you can add additional key buffers or (CACHE INDEXs) for individual tables after the server starts. You can read about this more here:

http://dev.mysql.com/doc/refman/5.0/en/multiple-key-caches.html

Later!

–Dave

By: Daniel Nuriyev

Daniel Nuriyev — Tue, 17 Apr 2007 16:08:45 +0000

I have 8Gb RAM with MySQL 5.0.27. Mistakingly I set key_buffer_size to 20Gb instead of 2Gb. Then I opened MySQL Administrator Health tab and saw there 4Gb of key_buffer_size. It seems that MySQL has some code that makes sure that key_buffer_size will not be more than the maximum.
Note: I set key_buffer_size through SET GLOBAL key_buffer_size = …; SQL command. I did not do it through a configuration file.

By: David W. Juntgen

David W. Juntgen — Mon, 19 Mar 2007 22:26:12 +0000

Peter,

If you would like to force mysql to lock itself into memory you can. This is useful to avoid page swaping. The down fall is that you must run as root and it sucks up all the memory defined by your my.cnf file for MyISAM and Innodb buffer pools. So, if you have a 6G key buffer, then you top will show a RES of 6G.

In your my.cnf file add these two lines under [mysqld]

user=root
memlock

–David

By: sean

sean — Wed, 14 Mar 2007 23:48:52 +0000

Peter,
Is there a way to monitor the usage and efficency of multiple key caches? Perhaps something similar ‘key_reads’ and ‘key_read_requests’.

By: peter

peter — Sun, 25 Feb 2007 20:48:36 +0000

Sean, As you found out yourself, yes this is the workaround you can use

By: Sean

Sean — Sun, 25 Feb 2007 20:23:26 +0000

My bad Peter, didn’t see your comment above

By: Sean

Sean — Sun, 25 Feb 2007 20:22:05 +0000

Peter,

Though I haven’t tried it, can one create multiple key caches up to 4 GB of memory as a work around?

By: An Expert's Guide to Oracle Technology

An Expert's Guide to Oracle Technology — Fri, 16 Feb 2007 16:56:28 +0000

Log Buffer #32: a Carnival of the Vanities for DBAs…

Welcome, to the 32nd edition of Log Buffer, the weekly survey of database blogs. What shall I talk about? Hmmm, maybe I’ll start with the Oracle blogosphere. Might as well get started with controversy by reading an entry by Dean……