[Plugin: W3 Total Cache] Hostname:port / IP:port

Your hosting provider should have provided it. Keep in mind that unless you have a multiple server configuration memcached is not the best caching method for all cases.

I installed memcached and got this error, too, even though phpinfo() showed it to be running. I fixed it by following the instructions under W3TC’s installation tab to properly initialize it. (It’s a standalone program rather than an extension like APC.)

I remember reading at some point that memcached would be better than APC for the object caching — is this true? I don’t have multiple servers, but I do have multiple WordPress installations (in a VPS), all running W3TC. I’m using APC for database caching and memcached for object caching.

(I’m not using the other features because I’m not worried about speed so much as CPU and memory usage.)

Revision (bug?): Setting all 4 WP installations to use memcache for object caching cause all but 1 to be blank. I changed 3 to use APC, leaving the busiest one to use memcached. Maybe I should change its database caching to memcached, too?

I remember reading at some point that memcached would be better than APC for the object caching — is this true?

No idea where you read that, it’s not true. All things are relative.

Revision (bug?): Setting all 4 WP installations to use memcache for object caching cause all but 1 to be blank. I changed 3 to use APC, leaving the busiest one to use memcached. Maybe I should change its database caching to memcached, too?

None of the caching engines have been changed significantly in some time, so I don’t understand what bug you mean.

Object caching creates lots of slabs in memcached and you could simply be having excessive cache misses or any number of things that are hard to guess without debugging. If you can your best bet is to give each type of cache it’s own memcached instance if for some reason you are compelled to use memcached for your case.

Sorry for the confusion: the revision I meant was of my earlier statement of using memcache. Thanks for the reply.

Ok, did I answer your question?

Configuring memcached is beyond my capabilities, I think. In the end, although W3TC did speed things up quite a bit, the overhead proved to be too much and I have disabled it, since we really needed to cut down RAM and CPU usage. I did, however, copy the browser cache settings as a starting point for the main site htaccess file, for which I thank you.

@ericr23 The best way to cut down on RAM and CPU usage would be to enable page caching using disk enhanced.

For Memcached to work you have to have the Memcached module installed (which sounds like you do) and the Memcached server installed which you can do following the Memcached (Daemon) installation instructions in the plugin.

@c3mdigital is right, page caching itself is likely the best way to free more resources on your server. While the cache is being built, you will have CPU usage just as you would while not having caching. Use the cache priming feature then move on to tune the user experience of the site by using other types of caching.

Hi,
I also have a single dedicated server, I received the same error as above with memcache and so now I’m reverting to use APC.

I have a question abotu c3mdigital’s post – “The best way to cut down on RAM and CPU usage would be to enable page caching using disk enhanced.”

is that correct – the most efficient caching from the perspective of RAM and CPU would be disk enhanced?
Any idea of the relative benefits/deficiencies of the various caching methods? I.e. APC is more memory/CPU intensive but is also faster?

Thanks

Thank also to Frederick for not only creating a great plugin but for taking the time to respond to questions in this forum.

Operating systems are designed to work with files on the disk (for the purposes of this conversation). The benefit of memory caching is great for lots of cases, but without writing a book. Using disk enhanced page caching puts the performance bound of your server with apache (and the efficacy .htaccess directives you have) instead of on PHP which is further (down) the stack (and therefor slower).

Thanks Frederick, I will just try them both and see what works.

Any luck?

APC seems to provide better response.
From pingdom.com
APC: initial page load : 1.2-1.6 seconds
Enhanced Disk: 1.6-1.8

I haven’t done enough iterations to check this thoroughly but initial impressions favor APC (at least in a non-stressed scenario).

note the above is the page load of my blog homepage only.

Overall using W3TC page loads decreased from around 5.5 – 6 seconds to 1.7 – 2.2 seconds. Biggest single factor seemed to be CDN implementation, but improvement is pretty widespread.