Configuring Apache/PHP/MySQL for Low Memory (RAM) VPS

As you known, I’ve moved from HostGator to DigitalOcean for two months and I shared some tips to build your own perfect LAMP server optimize for WordPress. With the VPS expansion you can now get a (very) small virtual private server (VPS) for a very affordable price. However, when you get a server with something like 256MB or 512MB RAM and a portion of CPU power, using default MySQL/PHP/Apache settings is a pretty bad idea. Currently, I’m running 3 websites with DigitalOcean‘s lowest plan: 512MB RAM/1 CPU. Not sure for load, but lets say 5-10k visitors per day.
If you follow my guidelines in previous post, RAM usage will be increase up to 400 MB then running out in 1 – 2 weeks even you turned on swap. How to minimize memory usage on LAMP to prevent your server crash?
I’ve setup a working VPS Ubuntu 12.04 LTS, LAMP server in 512MB of memory and it hasn’t gone into swap yet. It typically runs in just over 256 – 378Mb of memory and performs really well. So I thought I’d share the process of setting it up.

[digitalocean]

Determining Free Memory and Swap Activity

Before start optimizing your server, let’s review memory using on it. You can use the following command to display memory:

$ free -m

To see a list of your running processes sorted by memory use:

$ ps -eo pmem,pcpu,rss,vsize,args | sort -k 1 -r | less

Setup LAMP Server in a Low Memory Situation

Stop, Disable unused services

The first and obvious question to ask was what services do I not need? I recently discovered sysv-rc-conf that actually manages to nail the simplistic service management paradigm I was really looking for – by using freaking checkboxes:

Configure Linux Startup Applications with sysv-rc-conf
Configure Linux Startup Applications with sysv-rc-conf

Here is list of services which I’ve changed:

  • Postfix: This service let you sending & receiving email to your domain. I’m using Google Apps for emails and Mailchimp to manage newsletter’s subscribers. So I stop and disable Postfix server.
  • Bind9: You can manage domain record with bind9 service, it’s stoped & disabled since I used Digital Ocean DNS services.
  • SSHD: There are other implementations of sshd that use less memory, however the ones I considered did not support sftp and I need that, so I’m sticking with the standard install.

Don’t run X, shutdown all unneccesary services, and compile Apache, MySQL, and PHP with only essential functionality.

Apache

The biggest problem with Apache is the amount of ram is uses. I’ll discuss the following techniques for speeding up Apache and lowering the ram used.

  • Handle Fewer Simultaneous Requests
  • Loading Fewer Modules
  • Log less

Tune Apache to only have a small number of spare children running.

Prefork is where the real magic happens. This is where we can tell apache to only generate so many processes. The defaults here are high it’s eating your server memory. Make your sure apache2.conf is not configured to start too many servers, or have to many spare server best weight loss sitting around. Reference the example below:


    StartServers          1
    MinSpareServers       1
    MaxSpareServers       3
    MaxClients           10
    MaxRequestsPerChild 3000



    StartServers          1
    MinSpareThreads       5
    MaxSpareThreads      15 
    ThreadLimit          25
    ThreadsPerChild       5
    MaxClients           25
    MaxRequestsPerChild 200

Also, make sure to adjust KeepAliveTimeout to 10 or 15. In my opinion, 15 seconds is longer than a short page view requires, and shorter than a long page view requires.

Only load the modules you require

The default configuration file for apache also frequently loads every module it can. This is an especially big deal with the prefork mpm, as each apache instance will eat up geometrically more memory when unneeded modules are enabled. To check which apache modules are enabled/installed, use command below:

# apache2ctl -M

Default Apache modules (may be difference with yours):
Apache Loaded Modules
Here is list of Apache Modules which must be enabled for running WordPress:

LoadModule dir_module modules/mod_dir.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule mime_module modules/mod_mime.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule alias_module modules/mod_alias.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule rewrite_module modules/mod_rewrite.so

Comment out any modules that aren’t needed to save yourself some more memory. Or you can change it by use commands below:
To enable a module:

# a2enmod module_name

To disable a module:

# a2dismod module_name

You must restart the server after enable/disable the modules:

# service apache2 restart

Log Less

If you’re trying to maximize performance, you can definitely log less. In my server, I set it to error lever. Also, if you don’t care about looking at certain statistics, you can choose to not log certain things, like the User-Agent or the http-referer.

# ErrorLog: The location of the error log file.
# If you do not specify an ErrorLog directive within a 
# container, error messages relating to that virtual host will be
# logged here.  If you *do* define an error logfile for a 
# container, that host's errors will be logged there and not here.
#
ErrorLog ${APACHE_LOG_DIR}/error.log

#
# LogLevel: Control the number of messages logged to the error_log.
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
#
LogLevel error

I like seeing those things, but it’s up to you.

Optimize MySQL server

Tweaking MySQL to use small amounts of memory is fairly straightforward. I’m going to try to show you the why instead of the what, so you can hopefully tweak things for your specific server. We’ll look at the following MySQL types of mysql settings:

  • Things We Can Disable
  • Turning MySQL Server Parameters
  • Third Party Configuration Wizard for MySQL

To optimize mySQL we need to edit the mySQL configuration file, it’s /etc/mysql/my.conf

Things We Can Disable

MySQL allows a few different storage engines for its tables. The two most common are InnoDB and MyISAM. The main difference between the two is:

  • MyISAM offers table-level locking, meaning that when data is being written into a table, the whole table is locked, and if there are other writes that must be performed at the same time on the same table, they will have to wait until the first one has finished writing data.
  • InnoDB, on the other hand, offers row-level locking, meaning that when data is being written to a row, only that particular row is locked; the rest of the table is available for writing.

The problems of table-level locking are only noticeable on very busy servers. For the typical website scenario, usually MyISAM offers better performance at a lower server cost.

If you decide to use only MyISAM tables, you must add the following configuration lines to your my.cnf file:

default-storage-engine=MyISAM
default-tmp-storage-engine=MyISAM

If you only have MyISAM tables, you can disable the InnoDB engine, which will save you RAM, by adding the following line to your my.cnf file:

skip-innodb

If you use InnoDB from the past, here is a simple shell script to automatically convert InnoDB tables to MyISAM.

#!/bin/bash

MYSQLCMD=mysql

for db in `echo show databases | $MYSQLCMD | grep -v Database`; do
        for table in `echo show tables | $MYSQLCMD $db | grep -v Tables_in_`; do
                TABLE_TYPE=`echo show create table $table | $MYSQLCMD $db | sed -e's/.*ENGINE=\([[:alnum:]\]\+\)[[:space:]].*/\1/'|grep -v 'Create Table'`
                if [ $TABLE_TYPE = "InnoDB" ] ; then
                        mysqldump $db $table > $db.$table.sql
                        echo "ALTER TABLE $table ENGINE = MyISAM" | $MYSQLCMD $db
                fi
        done
done

Turning MySQL Server Parameters

There are several parameters that can be adjusted on a MySQL server to make it faster.

Key buffer size

This is probably the single most important thing you can tweak to influence MySQL memory usage and performance. MySQL tries to put everything that’s indexed into the key buffer so this is a huge performance speedup. The SQL query will be served directly from RAM. I can’t say what size you should make your key buffer, because only you know how much ram you have free.

The Query Cache

If you do the same query two times in a row, and the result fits in the query cache, mysql doesn’t have to do the query again. If you’re going for performance, this can be a huge benefit, but it can also eat up memory. So, you need setting it’s not too high and low as your website needed.
There are three variables that influence how the query cache works.

  • query_cache_size
  • query_cache_limit
  • query_cache_type

Maximum Number of Connections

It’s option parameter. If you’re already limiting the number of apache processes, then you’ll be fine. If you’re not, and you need to handle thousands of users simultaneously, you need to increase this number.

The Table Cache

Every time you access a table, MySQL loads a reference to a table as one entry in the table cache. This is done for every concurrent access of a table, it’s really important for performance, marginally so for memory usage. You can keep upping the table cache, but you’ll eventually hit a limit on the number of files your operating system can have open, so keep that in mind. If table cache is set too low, mysql will barf on you, and you don’t want that.
Here is current my.conf that I’ve optimized on my VPS with lowest Digital Ocean plan.

[mysqld]
     port            = 3306
     socket          = /var/lib/mysql/mysql.sock
     skip-locking
     key_buffer = 16K
     max_allowed_packet = 1M
     table_cache = 4
     sort_buffer_size = 64K
     read_buffer_size = 256K
     read_rnd_buffer_size = 256K
     net_buffer_length = 2K
     thread_stack = 64K

     # For low memory, InnoDB should not be used so keep skip-innodb uncommented unless required
     skip-innodb

     # Uncomment the following if you are using InnoDB tables
     #innodb_data_home_dir = /var/lib/mysql/
     #innodb_data_file_path = ibdata1:10M:autoextend
     #innodb_log_group_home_dir = /var/lib/mysql/
     #innodb_log_arch_dir = /var/lib/mysql/
     # You can set .._buffer_pool_size up to 50 - 80 %
     # of RAM but beware of setting memory usage too high
     #innodb_buffer_pool_size = 16M
     #innodb_additional_mem_pool_size = 2M
     # Set .._log_file_size to 25 % of buffer pool size
     #innodb_log_file_size = 5M
     #innodb_log_buffer_size = 8M
     #innodb_flush_log_at_trx_commit = 1
     #innodb_lock_wait_timeout = 50

     [mysqldump]
     quick
     max_allowed_packet = 16M

     [mysql]
     no-auto-rehash
     # Remove the next comment character if you are not familiar with SQL
     #safe-updates

     [isamchk]
     key_buffer = 8M
     sort_buffer_size = 8M

     [myisamchk]
     key_buffer = 8M
     sort_buffer_size = 8M

     [mysqlhotcopy]
     interactive-timeout

Third Party Configuration Wizard for MySQL

I’ve found Percona provide a free Configuration Wizard for MySQL that help you choose the best features of MySQL server to achieve better MySQL database performance and avoid the time, complexity, and risk of customizing a my.cnf configuration on your own.

MySQL Server Monitor

MySQL stores statistics that will help you to determine the best values that you must use. Furthermore, there are two handy utilities that can be used to read these statistics and print them on an easy-to-understand format: tuning-primer.sh and mysqltuner.pl.

These scripts will monitoring your MySQL server, at the end of its report, give you a hint of the parameters you should adjust on your server.

Optimize PHP & Caching

PHP is not very memory intensive, so I don’t think you should worry too much about memory usage, unless your app needs it, in which case the memory footprint of PHP won’t be too significant. But I’ve researched then found some tweaks of PHP configuration that decrease memory usage of your webserver.

; Limit the memory to 40M should be fine for barebones WordPress
memory_limit = 48M
realpath_cache_ttl=300
realpath_cache_size=1M

Alternative PHP Cache

Install a PHP Cache such as Alternative PHP Cache. The PHP cache will store compiled PHP scripts so that they can be reused without the overhead of compiling and processing them for each request.

# pecl install apc

And my php.ini configuration

[APC]
extension=apc.so
apc.enabled=1
apc.shm_segments=1

;32M per WordPress install
apc.shm_size=128M

;Relative to the number of cached files (you may need to watch your stats for a day or two to find out a good number)
apc.num_files_hint=7000

;Relative to the size of WordPress
apc.user_entries_hint=4096

;The number of seconds a cache entry is allowed to idle in a slot before APC dumps the cache
apc.ttl=7200
apc.user_ttl=7200
apc.gc_ttl=3600

;Setting this to 0 will give you the best performance, as APC will
;not have to check the IO for changes. However, you must clear 
;the APC cache to recompile already cached files. If you are still
;developing, updating your site daily in WP-ADMIN, and running W3TC
;set this to 1
apc.stat=1

;This MUST be 0, WP can have errors otherwise!
apc.include_once_override=0

;Only set to 1 while debugging
apc.enable_cli=0

;Allow 2 seconds after a file is created before it is cached to prevent users from seeing half-written/weird pages
apc.file_update_protection=2

;Leave at 2M or lower. WordPress does't have any file sizes close to 2M
apc.max_file_size=2M

;Ignore files
apc.filters = "/var/www/apc.php"

apc.cache_by_default=1
apc.use_request_time=1
apc.slam_defense=0
apc.mmap_file_mask=/var/www/temp/apc.XXXXXX
apc.stat_ctime=0
apc.canonicalize=1
apc.write_lock=1
apc.report_autofilter=0
apc.rfc1867=0
apc.rfc1867_prefix =upload_
apc.rfc1867_name=APC_UPLOAD_PROGRESS
apc.rfc1867_freq=0
apc.rfc1867_ttl=3600
apc.lazy_classes=0
apc.lazy_functions=0

Static Cache

Another thing that could be a great idea for a blog on a small server is to put it behind a static-HTTP-cache like Varnish. That can really boost your scalability. Configuring Varnish is a complex and large topic that requires its own blog post, however.

Conclusion

I’ve shared my webserver configuration to get best perfomance with lowest Digital Ocean’s droplet: 512MB RAM/1 CPU. I’m using Ubuntu 12.04 LTS, LAMP, Varnish, APC Cache to hosting 3 WordPress website (not Multisite) and alive with 10k visitors per day. Let’s see the Blitz.io test result:

Blitz Test Result
Blitz Test Result

As you see, 0.23% of the users got Connection Timeout when my website has 42,735,587 hits/day (WoW), may I have somethings to do but I’m feel pleasure with my server.
If you feel tired with this guide or don’t want do it by hands, let’s try PuPHPet or Vagrant

46 thoughts on “Configuring Apache/PHP/MySQL for Low Memory (RAM) VPS”

  1. Thanks for the guide. Simple enough for a newbie like me, but I’m still using a lot of RAM without any traffic on my wordpress site. Are you hosting this site (Narga) on a VPS with these settings?

    Do you have any more tips for optimizing Ubuntu in general? Not just Apache/PHP/MySQL.

    • Yes, I’m running 5 website (3 WordPress, 1 AnchorCMS, 1 PHP gallery, 1 static website) with lowest plan. It’s recevied 6-10k pageviews per day. Currently I use LAMP (ZPanel), Varnish, PHP Memcache. The maximium process of Apache are 3 process, MySQL server with smallest configuration.
      The biggest proccess that uses most server resource is Varnish, it’s cost my server about 18.6% MEM and 1.2% CPU.
      Everything was cached.
      Are your turned on the swap? Have you re-config apache to get lowest wordkers?

      • Hmmm I will have to check out those caches (or what about wordpress cache plugins?). But my site has no traffic yet, just testing, so I don’t know how much caching will help.

        I don’t have swap turned on. I heard it’s not good on a VPS. I did configure Apache and it saved a little more RAM. I might need to disable some more Apache modules.

        Thanks anyway.

  2. Nice tips, i can sure use some of these.
    I have one wordpress running on a 512MB droplet too.
    With LAMP and for some reason my MySQL server was constantly stopping, so i was getting “fail to connect to database” almost everyday. So i search in the web for solutions and ended up removing apache and using ngnix and since them everything is working fine.
    Now with the tips that you posted i guess i wont have any problems in the future since i don’t even get half of those daily hits.

  3. Impressive. I had trouble with the lowest plan but I was looking for these performance tweak. Something I should definitely test, can save a money with this!

  4. Nice – I’ll try some of these things even though I’m running a LEMP server, not Apache. Currently /usr/sbin/mysqld is using the most Memory/Virtual Memory on my server.
    My droplet says it’s using 44% of memory but then when I look using ps -eo pmem,pcpu,rss,vsize,args | sort -k 1 -r | less it shows maybe 10% of actual memory being used and VSZ is looking large (though I’m not sure).
    /usr/sbin/mysqld is using 327364 Vsize… is that a lot?

    Also wanted to point out that, at least for me, it’s /etc/mysql/my.cnf not /etc/mysql/my.conf

    • Yes, LEMP is better than LAMP if it has optimized but you will find some problem with .htaccess, scripts … because it’s wrote for Apache only.
      I’m not find the way to view droplet’s memory usage from DO CP but I think the result of system command is correctly.
      My file /etc/mysql/my.conf because I’m using Arch Linux, if you use Ubuntu it’s called as /etc/mysql/my.cnf :D

  5. Hi
    Thanks for your great article. I have optimized as you suggested. At the end I did blitz testing and I am facing issues.

    Initially I got lot of 502 error when I checked my error logs in nginx. so i found out that through this post about the issue that its common if you are not using TCP port for php :
    http://stackoverflow.com/questions/10470109/error-502-in-nginx-php5-fpm

    so now I used TCP port for php-fpm but now I am getting timeouts saying “worker_connections are not enough while connecting to upstream”

    Could you tell me how you achieved such great blitz result in your droplet. What settings are you using in nginx and php.

    Thanks. Looking forward to your reply.

  6. In the last line of this article you mentioned a link to PuPHPet and Vagrant. It would have been nice to include a configuration file similar to yours for use with these services. I am on one of those 512MB plans with DO and i keep getting database connection errors with my site (with 1 visitor, me).

    What you have done with your configuration is almost magical. Honestly. I have been struggling to fix this issue, i gave up and switched to Nginx. The problem is gone but i fear it my return with more load.

    How about writing a ‘How-to’ articles with step by step instructions and terminal commands? That would be so helpful. This MySQL errors are VERY common with DO’s 512 vps solutions and you would help ALOT of people.

    • As I mentioned above. I’m using DO with lowest plan like you: 1 CPU, 512MB RAM, Ubuntu 12.04. It’s running 3 sites and has about 10k visitors per day but last boot time of that droplet from 5 months ago. That is unbelievable but it’s true.
      I agree with you that MySQL is most problem and it’s eating too much memory but you can control it with my suggest configuration above. Let’s trying it with step by step, don’t copy and past whole file content.
      Are you using Ubuntu 12.4 or later version? May be it’s one cause of your problems.

      • @ Đình Quân Nguyễn… Thank for you response.
        Right now i am in the experimenting stage, getting familiar with managing my own server. As such i am researching and trying out many things, one of the experiments lead me to Nginx. I moved from Apache to Nginx and the problem is gone. I also did a Blitz.io rush the it held up well.

        After that i did ‘easygine’ and there setup also ran pretty well. Tomorrow i an trying ‘centminmod’. My sites are still on a shared hosting account so i have time to play around some more.

        BTW i am glad i found your article, it lets me know what i can expect from a similiar setup

  7. Hi,

    first of all, thanks for your article. I spent several days fighting with my Apache & MySQL because it died frequently, so I found your post very useful.

    I only want to add a link to an article on Digital Oceans about how to configure Varnish (between others): https://www.digitalocean.com/community/articles/how-to-install-wordpress-nginx-php-and-varnish-on-ubuntu-12-04

    Currently I’m using Apache because as you told, .htaccess is only for it, but I want to try to use wordpress with nginx as a challenge, maybe in another cheap-droplet :)

  8. So, and disabling Postfix without providing something alternative (msmtp) will make the system silent, very silent. Even system mails (e.g. cron) won’t make it everywhere. Maybe not a good idea. ;)

  9. StartServers          1
        MinSpareServers       1
        MaxSpareServers       3
        MaxClients           10
        MaxRequestsPerChild 3000
    
        StartServers          1
        MinSpareThreads       5
        MaxSpareThreads      15 
        ThreadLimit          25
        ThreadsPerChild       5
        MaxClients           25
        MaxRequestsPerChild 200
    

    I’m using your settings, but it hangs the server if there are more than 7 users simultaneously, what happen?

  10. wow, what a cool post
    i tried to do the tutorial, and i got a nice result

    would you tell me how to configure varnish for this tutorial?
    i am using a 1024MB digitalocean droplet + zpanel 10.1.1 + 3 wordpress site
    after installing varnish, i can’t open the ajaxplorer

    then i try to install pydio
    i can open pydio, but i can’t upload any files

    but while varnish removed, the ajaxplorer can be opened normally and upload file to pydio
    can you share the varnish configuration?
    thanks

    • You need configurate your varnish to ignore pydio, for example:

          ### do not cache these files:
          ##never cache the admin pages, or the server-status page
          if (req.request == "GET" &&
              req.request != "HEAD" &&
              req.request != "PUT" &&
              req.request != "POST" &&
              req.request != "TRACE" &&
              req.request != "OPTIONS" &&
              req.request != "DELETE" &&
          (req.url ~ "(wp-admin|bb-admin|server-status)")) {
            return(pipe);
          }
      
      • thanks
        i put these lines in varnish/default.vcl
        sub vcl_recv {
        if (req.url ~ "^/etc/apps/ajaxplorer/index.php") {
        return (pass);
        }
        if (req.url ~ "^/pydio/") {
        return (pass);
        }
        if (req.url ~ "^/usr/share/pydio/") {
        return (pass);
        }
        if (req.url ~ "^/usr/lib/pydio/") {
        return (pass);
        }
        if (req.url ~ "^/etc/apps/phpmyadmin/") {
        return (pass);
        }

        }

        now i can open pydio and upload any files
        but i can’t open archive file (zip) while using varnish
        so does the ajaxplorer, i can open ajaxplorer, upload files, but can’t open any archived (zip) files
        any suggestion?

    • Thanks for translated my article to russian. After moved to Digital Ocean, I started with LAMP but it’s eating too much memory so I switched to LEMP then it’s working perfectly.
      I’ve wrote some articles about LEMP installation and optimization, you can find it here or search for nginx keyword with Search Box on the topbar.

  11. Hi,
    with your configuration sometimes my site is down and in the apache log file I see this:
    [Thu Jan 15 11:33:26 2015] [error] server reached MaxClients setting, consider raising the MaxClients setting
    do you have a solution?
    I have tha same server as you have.
    Thank you so much great post.

  12. Hi, the inno_db_buffer_pool_size default is 8MB, do you recommend increasing this? I see some articles talking about incresing this to 64M. What do you recommend for less consuming?

    Thanks!

    • I’m not recommend because I prefer optimize it on a small and low RAM VPS, I’ve used for my old VPS with just 512MB of memory. If you increase it to 64MB, you’ll facing the blank of death of WordPress :D

  13. I am currently using opcache and I had already setup the MySQL to use much less memory.

    Just by using the first part of the Apache section of the post I was able to drop my memory usage down from 55% to 30%. Thanks a bunch =)

  14. I have 5 virtual servers and have maximum 10-20 real-time users and max 4k daily visitors. And the user can only interact with the website just to comment, no other data can be entered by the user.
    What would be the best configuration for it?

    My existing file apache and mysql configurations are following.

    StartServers 5
    MinSpareServers 5
    MaxSpareServers 10
    ServerLimit 8
    MaxClients 50
    MaxRequestsPerChild 1000

    StartServers 5
    MaxClients 100
    MinSpareThreads 1
    MaxSpareThreads 4
    ThreadsPerChild 25
    MaxRequestsPerChild 0

    And MySQL Config file is
    [mysqld]
    bind_address = 0.0.0.0
    datadir=/var/lib/mysql
    socket=/var/lib/mysql/mysql.sock
    user=mysql

    thread_cache_size=4

    join_buffer_size=4M
    sort_buffer_size=4M
    read_buffer_size=4M
    read_rnd_buffer_size=6M

    myisam_sort_buffer_size=32M

    key_buffer_size=32M
    tmp_table_size=32M
    max_heap_table_size=64M
    query_cache_size=64M

    query_cache_type=1
    default-storage-engine=myisam
    #skip-innodb

    [mysqld_safe]
    log-error=/var/log/mysqld.log
    pid-file=/var/run/mysqld/mysqld.pid

    Please Help.

    My resource configuration is –

    Operating system CentOS Linux 6.9
    Kernel and CPU Linux 2.6.32-042stab125.3 on x86_64
    Virtual memory 500 MB total
    Real memory 1000 MB total
    Local disk space 40 GB total / 36.90 GB free

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