Written by:

Zafar Mahmood
Database Solutions

Traditional Network Attached Storage solutions are usually deployed for the purposes for testing and developing databases due to their inherent performance limitations. Performance limitations arise due to additional overhead of managing the network file systems and their lack of scalability options. The NAS system has to be scalable and equipped with features such as a Scalable File System bundled with redundant cache optimized controllers in order to fit into the database storage eco system. This NAS solution is available in the form of Dell EqualLogic FS7500. Dell Database Solutions Engineering recently performed a study comparing the performance of an Oracle 11g R2 database running Online Transaction Processing workload between an iSCSI SAN and an Dell Equallogic FS7500 NAS. Let me first briefly introduce the FS7500 NAS storage solution.

The current release of the EqualLogic FS7500 product consists of up to two scalable pairs of FS7500 nodes and comes with a custom Backup Power Supply (BPS). It is based on Dell Scalable File System (DFS). Customers can purchase the FS7500 with an EqualLogic backend storage array for new NAS deployments or plug it seamlessly into an existing EqualLogic infrastructure to add NAS capability to the iSCSI based block storage. The key features of this appliance include a scale-out architecture, NFS v3.0, SMB 1.0, Snapshots, and Quotas; the major differentiator for database deployments is its capability to cache most recently used blocks into the RAM of the scalable pairs of nodes/controllers. Since the current release of the FS7500 supports up to two pairs in a single cluster, the caching capacity also scales as additional nodes pairs are added. The cache is synchronized between nodes/controllers to deliver optimal database performance for the NAS category of storage products. The backup power supply protects node/controller cache for safe flush to the backend storage array in case of accidental power outage.

Following diagram depicts a typical Oracle Real Application Clusters deployment scenario on FS7500 NAS storage: Figure1

The Dell EqualLogic FS7500 storage system is built with the idea of scalability and the added feature of offloading the file system management to the clustered file system management nodes/controllers with synchronized cache for the database volumes mounted by the database server nodes. Dell lab testing has shown that a single FS7500 node pair performs at par with a block storage solution such as an EqualLogic iSCSI system with same number of disks as shown in the figure 2. The diagram below shows that for up to a 1000 user load running an OLTP workload, the average query response time (which is one of the most important performance criteria for online transaction processing database systems) stays well within two seconds and on par with an iSCSI block storage solution. This type of response time is acceptable for most database systems.

Figure 3 shows another comparison from the perspective of transactions per second. From figure 8 one can observe that as we increase the user load on the database server nodes, both iSCSI and FS7500 systems exhibit comparable performance levels up to a 1000 user load after which the iSCSI solution still shows headroom for further user load. From these test results, you can conclude that the minimum configuration of the FS7500 storage system consisting of a single node pair can provide comparable performance to a block storage solution with same number of spindles and network IO ports. Also, the solution is scalable such that you are not limited to this performance level. You can add additional FS7500 nodes/controllers in pairs to achieve the required level of performance.

Figure 2:

Figure 3:

NOTE: The results we have provided are intended only for the purpose of comparison between two solutions consisting of specific configurations in a lab environment. The results do not portray the maximum capabilities of any system, database software, or storage.

The detailed white paper is available at the following link:

http://www.dell.com/us/enterprise/p/d/business~solutions~whitepapers~en/Documents~oracle-11gr2-rac-equallogic-FS7500.pdf.aspx