HP ProLiant 4500 Disk Subsystem Performance and Scalability - Page 18

WHITE PAPER (cont.) A discussion of RAID levels used in this white paper can be found in the "Preventing Data Loss While Maintaining Performance" section of this document. ECG025.0997 ... growth and increasing capacity requirements. For instance, choose the correct server configuration for your environment, yet leave slots available for future disk controllers that might be necessary to support future capacity requirements. Like Drive Scaling Like drive scaling is defined as comparing similar drives with the same RAID level and "scaling" or adding more drives to your system so that you can measure cumulative disk performance. Drive scaling can be summarized as the more drives you add to your system, the better the performance. However, the question you need to ask yourself is "When does the cost of adding more drives out weigh the performance gain?". To answer this question, Compaq tested controllers using the same RAID configuration and added drives, then measured the system performance effects. Let's now view those results and understand the effects of drive scaling. Like Drive Scalability Test Results Our one controller testing, illustrated in Figure 8, revealed that when using 2GB drives configured in a RAID 0 environment approximately a 50% performance increase was achieved when the drives were doubled. For example, we doubled the number of drives in the test configuration environment from 4 to 8 and experienced a 57% increase in performance. 20,000,000.00 18,000,000.00 16,000,000.00 14,000,000.00 Like Drive Scaling (RAID 0 - 1 Controller) 25% 12 x 2GB 8 x 2GB 4 x 2GB Server Throughput (Bytes/sec) 12,000,000.00 10,000,000.00 57% 96% 8,000,000.00 6,000,000.00 4,000,000.00 2,000,000.00 4 8 16 20 24 28 32 36 40 44 48 52 56 57 Number of Clients Figure 8: Like Drive Scaling in a RAID 0 Environment. In addition, we found when using 2GB drives in a RAID 5 configuration (4+1 vs. 8+1 drives), performance also increases over 50%. A performance increase was also obtained when using 4GB drives on one controller in either a RAID 0 or 5 environment. 18