On 2/27/09 8:50 AM, Pavel Aleksandrov wrote:
Hello, I am working for a big web site. We have around 9000 hits/s on
our MySQL replication trees and 500 000 unique visitors each day, just
to give a clue about the load we are experiencing. We run on MySQL,
Apache2, Gentoo, PHP 4 + PECL Memcache module. We've been using a
single 12G memcached instance for speeding up things (we've reached
the point where we can't solely rely on our DB). Using a single
instance is not what memcached is meant for, so we decided to scale
things up a bit, so we added 12 more instances, 2G each (32 bit
servers, 4 instances per server, 3 servers). Then we switched from the
"standard" (naive) method of hash distribution to the "consistent"
method.
What happened was that the load on our web nodes (we have 3 of them)
went up about 3 times the usual. I'm guessing it's the new hash
distribution method that's doing this. Am I missing something or using
this method is always so CPU intensive? Do we have another choice or
we should invest in more web nodes, to distribute the new load if we
decide to stick to the consistent hashing algorithm?
Are you really using PHP4? Not related just shocked.
Did you make all these changes at once?
--
Brian.
