Magento can sometimes be a beast to work with. Here are some notes:

Important Areas
==============

app/Mage.php - Has Version Info.
app/code/community/ - Plugins Go Here.
app/code/local - Custom Code Goes Here.
app/etc/modules - Modules Directory (less is best) 
../Cm_RedisSession.xml - Will want to modify this file if using Redis for Sessions
app/etc/local.xml - Set [DB / Session / Cache] Config

./cron.sh - trigger to run crons for magento

media/catalog - Great for NFS, some caching happens here  
var/log
var/report
var/cache
var/full_page_cache (Enterprise Edition)
var/session

Important Tables
==============

--core_config_data - Main Config Table
# SELECT * from core_config_data WHERE path LIKE "%some_setting%";
i.e. %url%, %redirect%, %secure%

--core_cache_option
# SELECT * from core_cache_option;
(should be 1)

--log_* ( If DB is very large maybe clean the DB Logs )
Admin Panel -> Advanced -> System -> Log Cleaning

Tuning
==============

Magento can do replication natively. (Not recommended cause its buggy - old school MySQL replication recommended)

[MySQL]
max_allowed_packet = 256M+
innodb_lock_wait_timeout = 200


ApacheBench Mark.
ab -c6 -n60 http:///index.html

OpCache PHP>=5.4
php55u-opcache
https://raw.githubusercontent.com/rlerdorf/opcache-status/master/opcache.php
/etc/php.d/10-opcache.ini

PHP MEM >= 512MB

Session and Cache
==============

** WANT TO KEEP CACHE AND SESSIONS SEPERATE **

IF wanting Sessions with Redis, will need to enable Redis in the following file:
../app/etc/modules/Cm_RedisSession.xml

Here is an example of a Redis Session and Redis Cache local.xml
local.xml.RedisSession.RedisCache.example.txt

---

Here we will use Memcache for Sessions and Redis for Cache. (prefered configuration, great for scaling)

local.xml.MemcacheSession.RedisCache.example.txt

** Good Idea to keep seesions in one place. No worry for latency.
** Large builds should have caches locally. Think network latency.
*** No need for Varnish. 

---

Load Balancing?

Make things easy by assiginging an Admin URL and give it a DNS Record
i.e. http://admin.mydomain.com - "A" Master Server IP
http://mydomain.com - "A" LB IP.
System -> Configuration -> Advanced -> Admin -> Admin Base URL

** Exclude var/sessions & var/cache from Lsyncd
** NFS ../media/*

Useful Redis Information
==============

Redis flush caches:
redis-cli -h  -p 6379 
redis> SELECT # (from redis-cli info # Keyspace)
redis> FLUSHDB

redis-cli monitor
redis-cli info


REDIS
/etc/redis.conf

disable -SNAPSHOTTING- (persistance)
maxmemory 1GB
maxmemory-policy allkeys-lru