Features of Web Cache

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Large web site operators know that Memcached yields substantial web site performance advantages. By providing a very high-density Memcached solution, Gear6 Web Cache provides even greater advantages.

Gear6 memory utilization technology enables the use of hybrid DRAM-flash memory configurations.  This memory architecture provides the high performance of DRAM and the very low cost of flash. Several times as much Memcached memory can be deployed in each “U” of rack space without increasing latency. Sophisticated slab management and eviction algorithms further extend these advantages, optimizing memory utilization and avoiding memory fragmentation issues that occur in many Memcached deployments.

For more information on the advanced memory utilization of Gear6 Web Cache, see the Save area of this site.

Scaling through high availability

Typical Memcached deployments do not comprehensively address web site requirements for high availability. Depending on your web architecture, a single failure can disable your web caches. Starting a new cache service to replace a failed one can take minutes, and restoring cache data until performance is again adequate can take hours.

This presents serious obstacles to scaling a large site, since you have to over-provision for failure events, and may feel the need to implement complex cache high availability into your applications.

Gear6 Web Cache is highly available out of the box. It is based on a powerful cluster architecture with numerous failover configuration possibilities. It can be configured for continuous service availability, meaning that the service, but not the cache data, is maintained in the event of a cache failure. It can also be configured for continuous data availability, meaning that a failed cache instance is immediately replaced with another instance that already contains the same cache data, so that normal operations continue throughout the failure incident.

For more information on the high availability features of Gear6 Web Cache, see the Protect area of this site.

Management and reporting

Reliably and smoothly scaling a web site is nearly impossible without good information. Standard Memcached software provides almost no visibility into the caching tier of your architecture. This means you have little decision data at your fingertips when there are problems, or when you’re considering new investments in Memcached to improve performance or to scale your site.

Gear6 Web Cache provides rich and easy-to-use Memcached management and reporting capabilities. Its management interface allows you to view aggregated service-level statistics, or to drill down at will to the level of individual instances or keys.

For more information on the advanced management and reporting capabilities of Gear6 Web Cache, see the Manage area of this site.

Save money, rack space, power and time

High-density DRAM-Flash Hybrid Architecture

Gear6 Web Cache introduces a substantial advantage in Memcached density by allowing high-speed DRAM and economical flash memory to be used in hybrid configurations. Advanced software memory management enables this hybrid operation, providing DRAM or near-DRAM performance for prices far below those of an all-DRAM solution, and without latency related to the use of flash memory.

The very high density of flash memory also means that 5-10 times as much Memcached memory can be deployed per “U” of rack space, reducing power consumption and cooling requirements as well as the cost and time involved in provisioning and managing hardware.

Optimized memory allocation

Besides the many benefits of its hybrid DRAM/flash architecture, Gear6 Web Cache employs a number of other technologies to reduce cost and boost Memcached performance.

Standard Memcached offers only a fixed selection of slab or “bucket” sizes that are typically not optimal for your, and you do not have any ability to modify them. The enhanced memory algorithms employed by Gear6 Web Cache replace standard Memcached memory management with a fine-grained block-based architecture that makes much more efficient use of memory.

Eviction management is another area where Gear6 Web Cache excels when compared to other Memcached solutions. They typically employ an LRU (“least recently used”) algorithm that overwrites cache data based only on how recently it was used, and without regard for how soon or how often it may be needed again. Gear6 Web Cache uses enhanced cost-based algorithms to make eviction decisions, caching the most frequently-used data. This increases cache hit rates and reduces the number of times data must be retrieved from storage (your database, file server or other source).

Gear6 Web Cache improves on Memcached memory management in other ways, for example, doing away with the 1 Mbyte Memcached object size limitation and allowing objects to be as large as desired.

Memory health monitoring and de-allocation

The best way to avoid failure-based web cache performance problems is to prevent or avoid failures before they happen. For this reason, Gear6 Web Cache employs a range of features that automatically and continuously scan both DRAM and flash memory for failures or failure indicators, removing affected memory from service as quickly as possible.

These algorithms take into account the different performance and reliability characteristics of DRAM and flash, and direct Gear6 Web Cache to use each in ways that maximize performance and reliability – for example, by not writing blocks of data across flash block boundaries when it can be avoided.

Information about memory health is also gathered in real time and provided to Gear6 Web Cache management interfaces for viewing and analysis.

Protect Your Users' Experiences & Site Performance

Continuous service availability through clustered architecture

Standard Memcached services are typically deployed across multiple hardware modules, but Memcached behavior is unpredictable if a module fails or some other failure occurs in the service. Instance IP addresses can vanish, triggering excessive latency or cascading failures.

Gear6 continuous service availability uses a clustering architecture that automatically fails over a failed instance to another available module. It keeps instance IP addresses alive and Memcached services functioning.

With continuous service availability, the service, but not not the cache data, is maintained in the event of a Memcached failure. This is the lowest-cost, highest-density way to deploy Gear6 Web Cache. It is suitable for applications where additional Memcached latency is acceptable after a failure has occurred, while new modules are loaded with cache data.

Gear6 Web Cache can also be configured for continuous data availability, so that normal operations continue without performance impacts throughout a failure incident. Learn more about continuous data availability.

Continuous data availability through replication

The continuous service availability features of Gear6 Web Cache automatically and transparently fails over to a new module when a module failure occurs, and normal operations resume as the new module is loaded with cache data.

But for some applications, cache performance may be unacceptably reduced as the rebuilding takes place. For this reason Gear6 Web Cache can also be deployed with replication, providing continuous data availability. With replication, cache data is always duplicated in another location, and when a module fails, the Memcached instance on the failed module is immediately replaced with another one already containing the same data. Memcached operations continue without interruption or slowdown. Spikes in database and application load are avoided.

Replication typically requires twice as much memory but is often justified for large and mission-critical applications. And because of the Gear6 Web Cache hybrid DRAM-flash architecture, a replicated Gear6 solution is typically still much less costly to purchase and operate than alternative Memcached solutions.

Fast, easy deployment without client-side modifications

If you’re using Memcached, you’re ready to take advantage of Gear6 Web Cache.

Gear6 Web Cache is 100% Memcached protocol-compliant, so any code that already works with Memcached is ready to take advantage of all the features of Gear6 Web Cache.

This means you can easily introduce Gear6 Web Cache to your environment, and gauge its value and ease of use.

All the other benefits of the Gear6 Web Cache solution, like hybrid DRAM/flash utilization, high availability and advanced management, are provided with no need for you to implement them in your code.

Code that works with standard Memcached works without modification with Gear6 Web Cache.

Disruption-free software upgrades

Maintaining and upgrading web cache servers can easily interfere with normal web site operations and the satisfaction of web site users.

Gear6 Web Cache software eliminates this problem. With it, caching tier software upgrades can be scheduled and performed without taking equipment out of service or affecting site performance.

The entire upgrade process can be controlled and observed through Gear6 Web Cache’s centralized management tools.

Manage Your Memcached operations

Advanced reporting with physical and logical aggregation and drill-downs

Reliably operating a complex web site is nearly impossible without good information. Standard Memcached software provides little visibility into the operation of your web caches. This means you have little decision data when there are problems, or when you’re considering new investments in Memcached to improve performance or to scale your site.

Gear6 Web Cache provides rich, easy-to-use management and reporting capabilities. Its management interface allows you to view aggregated performance statistics, or to drill down at will to the level of individual instances.

Hot key, client and instance reporting

A wealth of information and insight is provided through Gear6 Advanced Reporter. This insight can help architects, developers and administrators to pinpoint hotspots and bottlenecks, preventing or promptly resolving performance problems.

Advanced Reporter lets you easily see, for example, the top n keys in your caching tier. or the top n keys for any Memcached instance or client. This information useful for load balancing and architectural decisions.

Centralized management and administration

Management and administration of all Gear6 Web Cache resources is provided through an intuitive, browser-based management interface. Its capabilities are also available through a command-line interface (CLI).

With Gear6 Web Cache management you can create, view and edit instances and services, alerts, logs, version numbers, statistics and settings.