Add a FAQ file (it will also be used in the wiki).

FAQ

@@ -0,0 +1,90 @@
+# Some frequently asked questions about Predis #
+____________________________________________
+
+
+### What is the point of Predis? ###
+
+The main point of Predis is about offering a highly customizable client for Redis that can be easily 
+extended by developers while still being reasonabily fast. With Predis you can swap almost any class 
+used internally with your own custom implementation: you can build connection classes, or new 
+distribution strategies for client-side sharding, or class handlers to replace existing commands or 
+add new ones. All of this can be achieved without messing with the source code of the library and 
+directly in your own application. Given the fast pace at which Redis is developed and adds new 
+features, this can be a great asset that allows you to add new and still missing features or commands, 
+or change the behaviour of the library without the need to break your dependencies in production code 
+(well, at least to some degree).
+
+
+### Nice, but it is still a pure-PHP implementation: it can't be fast enough! ###
+
+It really depends, but most of the times the answer is: _yes, it is fast enough_. I will give you 
+a couple of easy numbers using a single Predis client with PHP 5.3.5 (custom build) and Redis 2.2 
+(localhost) under Ubuntu 10.10 (running on a Intel Q6600):
+
+    18500 SET/sec using 12 bytes for both key and value
+    18100 GET/sec while retrieving the very same values
+    0.210 seconds to fetch 30000 keys using _KEYS *_.
+
+How does it compare with a nice C-based extension such as [__phpredis__](http://github.com/owlient/phpredis)?
+
+    29000 SET/sec using 12 bytes for both key and value
+    30000 GET/sec while retrieving the very same values
+    0.037 seconds to fetch 30000 keys using _KEYS *_.
+
+Wow, __phpredis__ looks so much faster! Well we are comparing a C extension with a pure-PHP library so 
+lower numbers are quite expected, but there is a fundamental flaw in them: is this really how you are 
+going to use Redis in your application? Are you really going to send thousands of commands for each page 
+request using a single client instance? If so, well I guess you are probably doing something wrong. 
+Also, if you need to SET or GET multiple keys you should definitely use commands such as MSET and MGET. 
+You can also use pipelining to get more performances when this technique can be used.
+
+There is one more thing. We have tested the overhead of Predis by connecting on a localhost instance 
+of Redis, but how these numbers change when we hit the network by connecting to instances of Redis 
+that reside on other servers?
+
+    Using Predis:
+    3100 SET/sec using 12 bytes for both key and value
+    3100 GET/sec while retrieving the very same values
+    0.212 seconds to fetch 30000 keys using _KEYS *_.
+
+    Using phpredis:
+    3300 SET/sec using 12 bytes for both key and value
+    3300 GET/sec while retrieving the very same values
+    0.088 seconds to fetch 30000 keys using _KEYS *_.
+
+There you go, you get almost the same average numbers and the reason is quite simple: network latency 
+is a real performance killer and you cannot do (almost) anything about that. As a disclaimer, please 
+remember that we are measuring the overhead of client libraries implementations and the effects of the 
+network round-trip time, we are not really measuring how fast Redis is. Redis shines the best with 
+thousands of concurrent clients doing requests! Also, actual performances should be measured according 
+to how your application is going to use Redis.
+
+
+### I am convinced, but the performances of multi-bulk replies (e.g. _KEYS *_) are still worse ###
+
+Fair enough, but there is actually an option for you if you need even more speed and it consists on 
+installing __[phpiredis](http://github.com/seppo0010/phpiredis)__ (note the additional _i_ in the 
+name) and let Predis using it. __phpiredis__ is a C-based extension that wraps __hiredis__ (the 
+official Redis C client library) with a thin layer that exposes its features to PHP. You will now 
+get the benefits of a faster protocol parser just by adding a single line of code in your application:
+
+    Predis\Client::defineConnection('tcp', '\Predis\Network\PhpiredisConnection');
+
+As simple as it is, nothing will change in the way you use the library in your application. So, how 
+fast is it now? There are not much improvements for inline or short bulk replies (e.g. SET or GET), 
+but the speed for parsing multi-bulk replies is now on par with phpredis:
+
+    Using Predis with a phpiredis-based connection to fetch 30000 keys using _KEYS *_:
+
+    0.037 seconds from a local Redis instance
+    0.081 seconds from a remote Redis instance
+
+
+### If I need to install a C extension to get better performances, why not using phpredis? ###
+
+Good question. Generically speaking, if you need absolute uber-speed using localhost instances of Redis 
+and you do not care about abstractions built around some Redis features such as MULTI / EXEC, or if you 
+do not need any kind of extensibility or guaranteed backwards compatibility with different versions of 
+Redis (Predis currently supports from 1.2 up to 2.2, and even the current development version), then 
+using __phpredis__ can make sense for you. Otherwise, Predis is for you. Using __phpiredis__ gives you 
+a nice speed bump, but it is not mandatory.

README.markdown

@@ -4,8 +4,8 @@
 
 Predis is a flexible and feature-complete PHP (>= 5.3) client library for the Redis key-value store.
 
-For a version compatible with PHP 5.2 you must use the backported version of the latest release in the 0.6.x series.
-Please refer to the TODO file to see which issues are still pending and what is due to be implemented soon in Predis.
+For a list of frequently asked questions about Predis, see the __FAQ__ file in the root of the repository.
+For a version compatible with PHP 5.2 you must use the backported version from the latest release in the 0.6.x series.
 
 
 ## Main features ##