The default value of “Reserved block count” takes 5% of usable disk. On a large fs like 813G, it represents about 40G.
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 [...]

As you may know, when using memcached on 32-bit servers, processes can only address 4GB of virtual memory making the memcached daemon handle only 2 or 3 Gb of memory.
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 [...]

The dmidecode command gives you all informations available about your memory.
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 0×1000, 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 [...]