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Thursday
Oct292009

Paper: No Relation: The Mixed Blessings of Non-Relational Databases

This excellent survey of the field was written by Ian Thomas Varley as part of his Master of Science in Engineering program.

The aim of this paper is to explore the conceptual design space of non-relational databases as compared to traditional relational databases. It is clear that the design needs of the two paradigms are different, but how fundamental are the differences, and what strategies can we use to transition our conceptual designs from one to the other?
There are a few things to like about this paper. A running a example is used to show the different ways to model data depending on which type of solution you are targeting, especially covering how many-to-many relationships are modeled, data integrity, and how to support optional attributes. There's also a brief survey of some of the major systems.
The most interesting section of the report is where it tackles the problem of design for non-relational systems. The approach has two different phases: design questions and design strategies.
The questions you should ask yourself about your problem are:

Click to read more ...

Thursday
Oct292009

Digg - Looking to the Future with Cassandra

Digg has been researching ways to scale our database infrastructure for some time now. We’ve adopted a traditional vertically partitioned master-slave configuration with MySQL, and also investigated sharding MySQL with IDDB. Ultimately, these solutions left us wanting. In the case of the traditional architecture, the lack of redundancy on the write masters is painful, and both approaches have significant management overhead to keep running.

Since it was already necessary to abandon data normalization and consistency to make these approaches work, we felt comfortable looking at more exotic, non-relational data stores. After considering HBase, Hypertable, Cassandra, Tokyo Cabinet/Tyrant, Voldemort, and Dynomite, we settled on Cassandra.

Each system has its own strengths and weaknesses, but Cassandra has a good blend of everything. It offers column-oriented data storage, so you have a bit more structure than plain key/value stores. It operates in a distributed, highly available, peer-to-peer cluster. While it’s currently lacking some core features, it gets us closer to where we want to be than the other solutions.

continue... 

Wednesday
Oct282009

GemFire: Solving the hardest problems in data management

GemStone's website recently recieved a major facelift over at www.gemstone.com. I felt that the users of this site might find our detailed description of how we solve the hardest problems in data management interesting. This can be viewed at: http://www.gemstone.com/hardest-problems (PDF available for download).

Click to read more ...

Wednesday
Oct282009

And the winner is: MySQL or Memcached or Tokyo Tyrant?

Matt, from the ever excellent MySQL Performance Blog, decided to run a test using a simple scenario drawn from his client experience in the gaming space. The scenario: read a row based on a primary key, update the row, write it to disk, and use the row to lookup another row. Matt ran three different tests explained in a series of three different articles: MySQL and MySQL + Memcached, Memcached Only, and Tokyo Tyrant.

The lovingly compiled details along with many cool graphs are in the articles, but in general the lessons learned are:

Click to read more ...

Wednesday
Oct282009

Need for change in your IT infrastructure 

Companies earnings outstrip forecasts, consumer confidence is retuning and city bonuses are back. What does this mean for business? Growth! After the recent years of cost cutting in IT budgets, there is the sudden fear induced from increased demand. Pre-existing trouble points in IT infrastructures that have lain dormant will suddenly be exposed. Monthly reporting and real time analytics will suffer as data grows. IT departments across the land will be crying out “The engine canna take no more captain”. What can be done?

Click to read more ...

Monday
Oct262009

Facebook's Memcached Multiget Hole: More machines != More Capacity 

When you are on the bleeding edge of scale like Facebook is, you run into some interesting problems. As of 2008 Facebook had over 800 memcached servers supplying over 28 terabytes of cache. With those staggering numbers it's a fair bet to think they've seen their share of Dr. House worthy memcached problems.

Jeff Rothschild, Vice President of Technology at Facebook, describes one such problem they've dubbed the Multiget Hole.

You fall into the multiget hole when memcached servers are CPU bound, adding more memcached servers seems like the right way to add more capacity so more requests can be served, but against all logic adding servers doesn't help serve more requests. This puts you in a hole that adding more servers can't dig you out of. What's the treatment?

Click to read more ...

Sunday
Oct252009

Is Your Data Really Secured?

Caching/data-grids are going through a similar evolution to databases. As with databases, we started by using caching as an embedded service to the application. Now we are in the phase where we need to be able to share the data between multiple applications, or in cases where we don’t want to share the data, we need to be able to share the resources for managing the data, while keeping a high degree of isolation.

The demand for these sort of requirements becomes much more common with SOA or SaaS-based applications. As we approach the next generation of middleware and data-centers, it becomes clear that we cannot move to the next wave of virtualization and cloud computing without a strong security and isolation solution that is built-in to all layers of our application and middleware. 

Thursday
Oct222009

Paper: The Case for RAMClouds: Scalable High-Performance Storage Entirely in DRAM 

Stanford Info Lab is taking pains to document a direction we've been moving for a while now, using RAM not just as a cache, but as the primary storage medium. Many quality products have built on this model. Even if the vision isn't radical, the paper does produce a lot of data backing up the transition, which is in itself helpful. From the The Abstract:
Disk-oriented approaches to online storage are becoming increasingly problematic: they do not scale grace-fully to meet the needs of large-scale Web applications, and improvements in disk capacity have far out-stripped improvements in access latency and bandwidth. This paper argues for a new approach to datacenter storage called RAMCloud, where information is kept entirely in DRAM and large-scale systems are created by aggregating the main memories of thousands of commodity servers. We believe that RAMClouds can provide durable and available storage with 100-1000x the throughput of disk-based systems and 100-1000x lower access latency. The combination of low latency and large scale will enable a new breed of data-intensive applications.

Related Articles

Wednesday
Oct212009

Manage virtualized sprawl with VRMs

The essence of my work is coming into daily contact with innovative technologies. A recent example was at the request of a partner company who wanted to answer- which one of these tools will best solve my virtualized datacenter headache? After initial analysis all the products could be classified as tools that troubleshoot VM sprawl, but there was no universally accepted term for them. The most descriptive term  that I found was Virtual Resource Manager (VRM) from DynamicOps. As I delved deeper into their workings, the distinction between VRMs and Private Clouds became blurred. What are the differences?

Read more at: http://bigdatamatters.com/bigdatamatters/2009/10/cloud-vs-vrm.html

Monday
Oct192009

Drupal's Scalability Makeover - You give up some control and you get back scalability

Drupal 7 is having a scalability makeover. Karoly Negyesi, Drupal Core Developer and Public Development Team Lead, explains the process in this video: Drupal 7 APIs, scalability mindset. Karoly states the general theme of the changes as: You give up some control and you get back scalability. An interesting comment on the politics of scalability?

Makeover may not be quite the right word though. A makeover implies a cosmetic change, looking better by changing the surface. Drupal's changes will go deeper than that, right to Drupal's core. It's a genuine and authentic change that will hopefully allow one of the Internet's most venerable Content Management Systems (CMSs) to compete with a constant stream of younger and sexier models.

Drupal is based on an older LAMP stack approach where PHP modules are scooped up and merged together each time a request is made to Drupal. Drupal's most intriguing idea is how it is built, expands, and changes by weaving together a single system out of individual components called modules. Built-in modules include comments, RSS, contact forms, forums, and Clean URLs. Add in modules include things like CSE to add Google's Custom Search Engine, modules to add in AdSense, CAPTCHA, and Sitemaps. Drupal establishes AOP extension points that allow modules to work remarkably well together, creating a site that feels like one single site even though it has been constructed from dozens of modules hunted and gathered from all over the digital world. 

The problem is the PHP code can directly access the database and directly render to the UI, there is little required layering. Part of Drupal's amazing configurability and extensibility has been how easy it is for everything to work together by changing the database. But when there's no layering it's almost impossible to optimize the system. If you have 20 different modules they each can make 20 separate calls to the database when what we really want is one call. And because of the direct SQL access when the number of writes increases there's no systematic way to distribute the writes across multiple servers. So we see as Drupal sites grow in the number of modules and the number of users both performance and scalability tank.

The younger models architect their systems differently. Sites like Google, Amazon, Facebook are written terms of an API and a framework, a service based approach. Using a service based approach the web tier can be programmed in terms of services that themselves are scalable so the entire system is scalable. When the API is skipped there are no leverage points that can be made to scale. It becomes a big ball of mud.

More layering and more APIs is exactly the direction Drupal is taking. Exactly how is Drupal changing?

Click to read more ...