Web Hosting Talk : Web Hosting Main Forums : Hosting Security and Technology : Server has 7 GBs of free RAM

[Harzem]

Current server has 4 GB ram, all buffered by linux.

             total       used       free     shared    buffers     cached
Mem:          4054       3917        137          0         99       2139
-/+ buffers/cache:       1678       2375
Swap:         4094          0       4094

The buffer has 2375 MB of free ram. However this is a heavy mysql server. I want the empty ram be used by mysql so it becomes faster.

We are currently moving to a 8GB ram server, and the free ram will be around 7 GB if we use the exact same configuration. I want the free ram to be 1 GB at most, why pay for 8 GB ram if I'm going to use a fraction of it?

What optimizations should I attempt?

Notes:
- I know about harddisk I/O bottlenecks, I have two SATA drives in the system, and a SAS drive dedicated to mysql, that's all we can afford currently.
- All mysql databases are for SMF forums, and currently using MyISAM tables. Switching to another storage engine is a possibility, if it won't create problems in restarts and hot backups.

[Shain P]

You can clear the cached RAM by executing the following command as root

========================================
sync; echo 3 > /proc/sys/vm/drop_caches
========================================

[Harzem]

Great, but that's not what I'm asking at all Thanks for trying to help though!

[Shain P]

I'm sorry about that. That was the response to another post, got the tabs mixed up.

You can use the MySQL Tuner script for doing this

# wget http://mysqltuner.com/mysqltuner.pl
# chmod +x mysqltuner.pl
# ./mysqltuner.pl

This will let you know which Variables to adjust for optimum performance.

[Harzem]

Thanks, we are already using it, but it doesn't show us a way to populate the RAM for the best performance.

I was hoping to get a few more opinions from a few more people!

[Vinayak_Sharma]

Have you checked, where all the RAM is being used and how much RAM MySql is using?

[Harzem]

Originally Posted by vinsar

Have you checked, where all the RAM is being used and how much RAM MySql is using?

Yes, RAM is staying idle, as I posted in my first post. Not sure particularly how much MySQL is using, but I sure like it to increase, so it gets faster.

[foobic]

Are you using the query cache?

[Harzem]

Originally Posted by foobic

Are you using the query cache?

Is it an application level or a server-wide setting?

[foobic]

Server-wide. http://dev.mysql.com/doc/refman/5.1/en/query-cache.html

Trying to get it to use all your spare memory would probably be counter-productive, but it's certainly worth giving it something.

[Vinayak_Sharma]

Your total RAM is 4054, used is 3917 and free is 137 how come the server has 7 GB?

query cache is a MySql setting that you set in my.cnf

Is this a cPanel server
Can you post the /etc/my.cnf content here (remove the client/password section if it is in there)?

[luki]

You are already using that RAM for caching, so it's not just sitting there unused. The kernel takes care of caching for you on the block and file system level. The only place where you can cache things on mySQL itself is with the query cache, which works pretty well if your data has lots of repeating reads.

The mySQL tuning primer will tell you if you buffers are sufficiently large (for joins, sorting, etc). but these are used to process a query. Repeated access to the data on the disk itself is cached by the OS, so the more RAM you have for caching the better (you currently use 2.1 GB).

For comparison, my DB server has 16 GB of RAM, of which over 15 GB are just cached data. It handles about 20 million queries a day without breaking a sweat.

[Harzem]

Originally Posted by vinsar

Your total RAM is 4054, used is 3917 and free is 137 how come the server has 7 GB?

As I said in the first post, the new server will have.

I will try query cache and give it a few GBs of ram to use, and let you know the result, thanks

[M Bacon]

Is this a 32bit or 64bit OS?

[Harzem]

64 bit OS.