These blocks are reserved to the super user to recover from situations where user processes fill up filesystems.
It is absolutely safe to reduce this space to one hundred or so MB.

• check disk space of our filesystem:

$ df -h /dev/sda4
/dev/sda4             813G  418G  354G  55% /home

Before the tuning, we have 354G free.

• check the current number of reserved blocks:

$ tune2fs -l /dev/sda4
...
Reserved block count:     10816865
...

Change this number to 20000.
The blocksize is 4096, 20000 blocks represent about 80MB.

$ tune2fs -r20000 /dev/sda4
...
Reserved block count:     20000
...

• check disk space of our filesystem:

$ df -h /dev/sda4
/dev/sda4             813G  418G  395G  52% /home

We now have a gain of 40GB of free space!

If you want to address more memory, you need to launch multiple memcached daemons.

I wrote an rc script , mmemcached, for FreeBSD to manage this.

To use it, you need to add this in /etc/rc.conf:

mmemcached_enable="YES"
mmemcached_servers="1 2"
mmemcached_user="nobody"
mmemcached_args="-c 8192 -t 2 -m 2048 -d"

Copy the mmemcached script in /usr/local/etc/rc.d for example and launch it with the start argument. With the above configuration it will launch two memcached daemons listening on ports 11211 and 11212 (mmemcached_servers parameter) with 2Gb of memory.

Configuration

Details of the rc.conf configuration:

• mmemcached_enabled: let this script “startable”,
• mmemcached_servers: List of the daemons you want to start. Each number is used to generate the port number of the daemon. For example, 2 will launch a daemon listening on port 11212,
• mmemcached_user: user that will start the daemon,
• mmemcached_args: flags to pass to the daemon.

Download

Download the script on github.

With the special parameter “-t 16″, you can see the maximum (physical) memory that your server can have:

$ dmidecode -t 16
# dmidecode 2.8
SMBIOS 2.4 present.

Handle 0x1000, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Multi-bit ECC
Maximum Capacity: 32 GB
Error Information Handle: Not Provided
Number Of Devices: 8

Here we can see that your server can handle up to 32Gb

Check empty memory slots

To know which slots are used or not use the “-t 17″ flag.

dmidecode -t 17 | grep Size
        Size: 2048 MB
        Size: 2048 MB
        Size: No Module Installed
        Size: No Module Installed
        Size: No Module Installed
        Size: No Module Installed
        Size: No Module Installed
        Size: No Module Installed

Links

• DMI specification
• SMBIOS specification