On scaleio, xtremsw cache can be deployed in two ways:
- Xtremsw cache is used inside each server as cache-cache is implemented under scaleio Data Server (SDS), which is similar to the concept of vnx fast cache or Vmax cache in the traditional SAN world.
- Use the xtremsw cache on the application side as the cache-perform the cache under scaleio Data Client (SDC). This concept is similar to the server side caching in the data center.
Caching inside each server (caching below the SDS)
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The advantages of such configuration are as follows:
- Better Data Consistency: For applications with high data sharing requirements, data consistency is crucial. if one piece of data is replaced by an applicaiton host, another host in this environment is modifying the same piece of data on the shared storage. this situation may cause data destruction and various inconsistencies. by placing xtremcache under SDS, we can accelerate without such a risk, so that we can achieve consistency.
- No cold cache (cold cache): Because the cache is performed on the storage end rather than the application end, the cache will not be affected by the Failover of the application host. therefore, there will be no cold cache time to "push" (warm up), so the performance will be more stable. in many environments, failover does occur, not only because of errors (which can be considered as a rare occurrence ), there is also a Failover mainly for Server Load balancer. in the node cluster controlled by scaleio, this is very relevant because the computing resources in scaleio are flexible to the computing tasks.
- Better utilization of Cache: By deploying the cache under the SDS of each node, a large shared cache layer is generated, so that all applications in the cluster can use the cache. for example, you have 20 nodes, 20 different applications, and 20 GB xtremcache cards. you have a total of 7 TB flash cache. some applications use more cache, and some applications can use less cache to meet their needs-this is related to the size of the application's data set. by setting the cache in each server, you get a 7 TB flash cache that can be dynamically assigned to the user. therefore, for active applications that consume terabytes of cache, this can greatly increase the cache hit rate and overall performance.
Application side caching (caching abve the SDC)
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The cache is only deployed on an applicaiton server. The advantages of this configuration are as follows:
- Performance:If the environment is very sensitive to disk latency (an increase of a few milliseconds can be clearly reflected), this deployment method is more appropriate because the data is close to the application, the cache does not consume network bandwidth.
- Deployment considerations:The granularity of such deployment is finer. If only a few applications require acceleration, you can deploy xtremcache to accelerate a certain number of virtual machines, and there is no consistency problem mentioned above.
- Data Consistency:The cache card software must support data upload uption protection. xtremcache is native (supports Oracle RAC, and active/passive clusters such as MSC, VCs, or native Linux clustering ).
In short, either the xtrem card is deployed under SDS or SDC. deployed under SDS, scaleio is aware of the existence of the xtrem card. deployed on SDC, it has nothing to do with scaleio. What about scaleio.
Data Source
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The whole is greater than the sum
Http://www.scaleio.com/blog/entry/the-whole-is-greater-than-the-sum
