Redhat – Memcached inconsistency in values for maxbytes and limit_maxbytes

The short answer: Either one is what you are looking for, but my first choice would be memcache (the first one you listed), purely based on its correct use of nomenclature.

Now here's how I came to that conclusion:

Here is a quick backgrounder in naming conventions (for those unfamiliar), which explains the frustration by the question asker: For many *nix applications, the piece that does the backend work is called a "daemon" (think "service" in Windows-land), while the interface or client application is what you use to control or access the daemon. The daemon is most often named the same as the client, with the letter "d" appended to it. For example "imap" would be a client that connects to the "imapd" daemon.

This naming convention is clearly being adhered to by memcache when you read the introduction to the memcache module (notice the distinction between memcache and memcached in this excerpt):

Memcache module provides handy procedural and object oriented interface to memcached, highly effective caching daemon, which was especially designed to decrease database load in dynamic web applications.

The Memcache module also provides a session handler (memcache).

More information about memcached can be found at » http://www.danga.com/memcached/.

The frustration here is caused by the author of the PHP extension which was badly named memcached, since it shares the same name as the actual daemon called memcached. Notice also that in the introduction to memcached (the php module), it makes mention of libmemcached, which is the shared library (or API) that is used by the module to access the memcached daemon:

memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

This extension uses libmemcached library to provide API for communicating with memcached servers. It also provides a session handler (memcached).

Information about libmemcached can be found at » http://tangent.org/552/libmemcached.html.

In summary, both are functionally the same, but they simply have different authors, and the one is simply named more appropriately than the other.

What everyone else has noted about default installs is fairly true, though most eg CentOS systems have come out of the box running a basic firewall for some time now. But even a basic firewall will normally allow all connections from localhost to localhost, as is it extremely unwise to forbid these; the oddest things can start happening. If there's a line near the top of your INPUT chain (or any chain to which INPUT delegates the bulk of its work) that says

iptables -A INPUT -i lo -j ACCEPT

or in iptables -L -n -v format,

  840 97979 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0           

(never mind the first two fields, they're packet and byte counts and yours would of course be different) then you're probably OK. Another good test is to do

telnet localhost 11211

if you get

Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).

then you know your listener's running and the firewall's not blocking it. Failing that, give us your iptables -L -n -v and your netstat -an outputs, as the others suggest, so we can take a look.