Choosing the right caching solution for your application can significantly impact performance. When faced with the decision between Memcache and Memcached, understanding the nuances of each is crucial. While the names are similar, subtle differences can make one a better fit than the other depending on your specific needs. This post dives deep into the “Memcache vs. Memcached” debate, providing you with the information necessary to make an informed decision.

Understanding Memcache

Memcache, the older of the two, is a simple key-value caching system. It’s known for its speed and simplicity, making it ideal for caching small, frequently accessed data. Think of it as a quick lookup table for your application, storing data in memory to reduce database load.

Its primary focus is performance, achieved by minimizing overhead. However, this simplicity comes with trade-offs. Memcache doesn’t offer data persistence or redundancy. If the server restarts, the cache is wiped clean. Also, data distribution across multiple servers isn’t built-in, requiring manual configuration.

A key characteristic of Memcache is its use of consistent hashing, which helps distribute data evenly across multiple cache servers. This minimizes data loss when adding or removing servers from the cache cluster.

Exploring Memcached

Memcached builds upon the foundation of Memcache, adding valuable features while maintaining impressive performance. One significant addition is persistent storage options. While not default behavior, Memcached allows you to configure persistence to disk, safeguarding your cached data against server restarts.

Furthermore, Memcached boasts built-in data replication, enhancing both data availability and fault tolerance. If one cache server fails, replicas ensure continued operation, preventing data loss and application disruption. This feature is a boon for applications requiring high availability.

Memcached supports a wider range of data types than its predecessor. This includes storing larger values, allowing you to cache more complex objects. This increased flexibility can simplify application development and potentially reduce the number of database calls even further.

When to Choose Memcache

Memcache excels when simplicity and speed are paramount. If your application needs a fast, in-memory cache for frequently accessed small data, and data persistence isn’t critical, Memcache is often the best choice.

Consider these scenarios:

• Caching small, frequently accessed data like session variables or database query results.
• Environments where data loss upon server restart is acceptable.
• Applications prioritizing raw speed over advanced features.

For example, a high-traffic website serving primarily static content might benefit from Memcache’s speed, caching frequently accessed HTML snippets.

When to Choose Memcached

Memcached comes into its own when high availability and data persistence are essential. Its added features make it a robust solution for mission-critical applications where data loss is unacceptable.

Consider these situations:

• Caching larger objects or more complex data structures.
• Applications requiring data persistence to mitigate the impact of server restarts.
• Environments where high availability and redundancy are crucial.

For instance, an e-commerce platform processing thousands of transactions per minute would benefit from Memcached’s data replication and persistence capabilities, ensuring consistent performance and data integrity.

Key Differences at a Glance

Here’s a quick comparison to solidify the key distinctions:

1. Persistence: Memcached offers options for persistence, whereas Memcache does not.
2. Replication: Memcached supports built-in replication, while Memcache requires manual configuration.
3. Data Types: Memcached handles a wider range of data types and larger values compared to Memcache.

Making the Right Choice: A Practical Example

Imagine a social media platform. User session data, frequently accessed but not critical for long-term storage, could be efficiently managed by Memcache. However, user profile information, requiring persistence and high availability, would be better suited for Memcached.

[Infographic comparing Memcache and Memcached visually]

Frequently Asked Questions

Q: Can Memcache and Memcached be used together?

A: While not common, they can be used in conjunction, leveraging Memcache for specific high-speed caching needs and Memcached for other data.

Q: What are common client libraries for accessing these caching systems?

A: Popular libraries include libmemcached (for both) and various language-specific clients like pymemcache (Python) and php-memcached (PHP).

Choosing between Memcache and Memcached depends entirely on your application’s specific requirements. By carefully considering factors like data persistence, replication needs, and the nature of the data being cached, you can leverage the strengths of each system to optimize performance and ensure data integrity. Don’t just settle for the familiar name – choose the solution that truly fits your needs. Explore the documentation for both Memcache and Memcached to further refine your understanding and make the best choice for your next project. Learn more about optimizing your caching strategy and check out these additional resources: Resource 1, Resource 2, and Resource 3.

Question & Answer :
It seems that PHP has two memcached libraries named memcache and memcached. What is the difference and how do you know which one to use? Is one outdated? It seems that memcached offers more methods so I would assume that means it has had the most development - but it also seems to require external C/C++ libraries so I’m not sure if I can install it.

It seems that memcache has been around longer, does not require additional libraries, and has pre-compiled binaries for even windows! I would think that it would be the better choice for now. However, being new to memcached (server) I’m not sure if there is some super important features in memcached (php) that make it worth the extra trouble.

Memcached client library was just recently released as stable. It is being used by digg ( was developed for digg by Andrei Zmievski, now no longer with digg) and implements much more of the memcached protocol than the older memcache client. The most important features that memcached has are:

1. Cas tokens. This made my life much easier and is an easy preventive system for stale data. Whenever you pull something from the cache, you can receive with it a cas token (a double number). You can than use that token to save your updated object. If no one else updated the value while your thread was running, the swap will succeed. Otherwise a newer cas token was created and you are forced to reload the data and save it again with the new token.
2. Read through callbacks are the best thing since sliced bread. It has simplified much of my code.
3. getDelayed() is a nice feature that can reduce the time your script has to wait for the results to come back from the server.
4. While the memcached server is supposed to be very stable, it is not the fastest. You can use binary protocol instead of ASCII with the newer client.
5. Whenever you save complex data into memcached the client used to always do serialization of the value (which is slow), but now with memcached client you have the option of using igbinary. So far I haven’t had the chance to test how much of a performance gain this can be.

All of this points were enough for me to switch to the newest client, and can tell you that it works like a charm. There is that external dependency on the libmemcached library, but have managed to install it nonetheless on Ubuntu and Mac OSX, so no problems there so far.

If you decide to update to the newer library, I suggest you update to the latest server version as well as it has some nice features as well. You will need to install libevent for it to compile, but on Ubuntu it wasn’t much trouble.

I haven’t seen any frameworks pick up the new memcached client thus far (although I don’t keep track of them), but I presume Zend will get on board shortly.

UPDATE

Zend Framework 2 has an adapter for Memcached which can be found here