Hi,
Yes, you are right, it should read 1305MB and it should also have the buffers amount added; so another 148MB is available.
This is just how Linux reports the memory usage. The cached memory is usually what is used by the OS to cache file writes & reads to and from the hard drives. If you turn this off, you will most likely have performance issues. Buffers are normally used by the network adaptors to buffer incoming and outgoing traffic.
High cache values indicate that there is a lot of disk io occurring. This would be the case if you are running VOD applications or have a lot of recording going on. If the cache is consuming all of the memory, it may be indicating that you need faster disks or more memory.
Wowza Streaming Engine can only see the total and used values and reports based on these. It cannot see the cached or buffered values so cannot take these into account.
Roger.