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STORAGE45040035024%987Transactions per second30025020015010050~ 17% ~ 10%PowerVault 775N configurationMaximum MinimumResponse time (sec)654321Read-write ratio20:8050:5080:20001022043064085106127148169181,0201,1221,2241,3261,4281,5301,6321,7341,8361,9382,0402,1422,2442,3462,4482,5502,6522,7542,8562,9583,0603,1623,2643,3663,4683,5703,6721022043064085106127148169181,0201,1221,2241,3261,4281,5301,6321,7341,8361,9382,0402,1422,2442,3462,4482,5502,6522,7542,8562,9583,0603,1623,2643,3663,4683,5703,672User loadUser loadFigure 5. Effect of PowerVault 775N configuration on performance, using small file sizes and an 80:20read-write ratioFigure 6. Effect of read-write ratios on a maximally configured PowerVault 775N, using small file sizesnor does it indicate any type of failure. The number is simply the maximumlicensing limit within Benchmark Factory.Figure 5 shows that, as user load increased, the performancedifference between the minimum and maximum PowerVault 775Nconfigurations diminished. To benefit from the performance of a maximallyconfigured PowerVault 775N, storage administrators mayconsider adding another NAS server as user loads increase.The read-write ratio can significantly affect the performance ofa maximally configured PowerVault 775N, as shown in Figure 6. Forexample, when I/O requests averaged 80 percent reads at a user loadof 1,632, each user could expect the I/O request to be satisfied inapproximately 1.5 seconds. If the average I/O request was 80 percentwrites, each user could expect I/O requests to be satisfied inapproximately 4 seconds.Figure 7 can help storage administrators determine how manyPowerVault 775N servers they may need. For example, if a 15-secondresponse time is unacceptable in an environment with 1,530 userswho typically request large files and perform 80 percent reads and20 percent writes, an additional NAS server is recommended. Ifthe administrator implements and properly configures a secondPowerVault 775N such that the load is balanced between the twoservers, response times to each of the 1,530 users can decrease from15 seconds to 7 seconds. The reduction in response time can occurbecause the user load for each server decreases from 1,530 to 765.Achieving optimal PowerVault 77xN performanceIn this study, peak performance testing for the PowerVault 770Nidentified that PowerVault 770N resources become fully utilized at athroughput of 1011 Mbps. With an understanding of this result,administrators can effectively avoid overutilizing the PowerVault77xN, keeping its operation at a highly available and functional state.To help determine whether a PowerVault 77xN will perform ata satisfactory level for their specific enterprise configurations,Response time (sec)50454035302520151050File sizeLargeMediumSmall1022043064085106127148169181,0201,1221,2241,3261,4281,5301,6321,7341,8361,9382,0402,1422,2442,3462,4482,5502,6522,7542,8562,9583,0603,1623,2643,3663,4683,5703,672User loadFigure 7. Effect of file size on a maximally configured PowerVault 775N, using an 80:20 read-write ratioadministrators can consider the results from the scalability testingpresented in this article. These results can help administrators determinethe number of PowerVault 77xN servers required to achievesatisfactory NAS performance for a multitude of users.Ward Wolfram (ward_wolfram@dell.com) is a storage performance and solution engineeron the Dell Solution Enablement Lab and Technology Showcase team. His responsibilities includeperformance and best-practice analysis for storage area network (SAN), NAS, and tape backupsystems. Ward has an M.S. in Computer Science from the University of Nebraska at Lincolnand a B.S. in Mathematics from Concordia University in Seward, Nebraska.Philip Wong (philip_wong@dell.com) is a systems engineer in the Dell Enterprise PerformanceAnalysis Lab. His current projects include NAS systems performance tuning and industrystandardbenchmarking on the Red Hat Linux operating system. Philip has a bachelor’s degreein electrical engineering from the University of Pennsylvania.www.dell.com/powersolutions POWER SOLUTIONS 109