VERITAS VOLUME MANAGER™ FOR WINDOWS …eval.symantec.com/mktginfo/products/White_Papers/Storage_Server... · WHITE PAPER VERITAS Volume Manager™ for Windows 2000 VERITAS VOLUME

W H I T E P A P E R

VERITAS Volume Manager™ for Windows 2000

VERITAS VOLUME MANAGER™ FOR WINDOWS SOFTWARE VS. HARDWARE RAID PERFORMANCE February 2003

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TABLE OF CONTENTS Table of Contents…………………………………………………………………………………………………..…….……2 Summary………………………………………………………………………………………………….………………..…..3 Introduction…………………………………………………………………………………………….……………….….…..3 About the Benchmark………………………………………………………………………………………………….…...…3 About TPC-C…………………………………………………………………………………………………………………3 About SQLIO ……………………………………………………………………………………………………………..…3 Test Configurations……………………………………………………………………………………………………………3 TPC-C using Microsoft SQL Server 2000………………………………………………………………………………...3 Disk I/O Subsystem Test using SQLIO……………………………………………………………………………………4 Results………………………………………………………………………………….………………………………………4 RAID 0 TPC-C VM vs. Brand X RAID Card………………………………………………………………………………4 RAID 0 TPC-C VM vs. Brand Y RAID Card………………………………………………………………………………5 RAID 0 SQLIO VM vs. Brand X RAID Card………………………………………………………………………………6 RAID 5 TPC-C VM vs. Brand X RAID Card………………………………………………………………………………7 RAID 5 TPC C VM vs. Brand Y RAID Card………………………………………………………………………………8 RAID 5 SQLIO VM vs. Brand X RAID Card………………………………………………………………………………9 Conclusion…………………………………………………………………………………………………………………….11 Appendix………………………………………………………………………………………………………………………12

Copyright © 2003 VERITAS Software Corporation. All rights reserved. VERITAS, the VERITAS Logo and all other VERITAS product names and slogans are trademarks or registered trademarks of VERITAS Software Corporation. VERITAS, the VERITAS Logo Reg. U.S. Pat. & Tm. Off. Other product names and/or slogans mentioned herein may be trademarks or registered trademarks of their respective companies. Specifications and product offerings subject to change without notice.

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Summary This paper summarizes the performance study comparing VERITAS Volume Manager™ for Windows 2000 to hardware RAID 0 and RAID 5, based on:

• Light to moderately stressed systems, software RAID 5 performance is comparable to the high-end hardware RAID card and is significantly better than the midrange hardware RAID card.

• Software RAID 0 performance is comparable to the high-end hardware RAID 0 and is 10 percent better than the midrange hardware RAID card.

Potentially, using VERITAS Volume Manager™ for Windows 2000 software in configuring RAID will offer comparable or better performance without the extra hardware cost. Volume Manager provides domainwide online storage management, capacity monitoring and storage load balancing from a single Windows 2000 console. Introduction The VERITAS Volume Manager™ for Windows 2000 provides a comprehensive solution to storage management in an integrated graphical view. With a common interface, Volume Manager lets you configure and manage local and remote storage attached to your system, while your system remains online. Through the Volume Manager console, the user can create and configure software RAID devices while systems remain online and available, optimize storage performance via online capacity monitoring and storage load balancing and manage domainwide storage from a single Windows 2000 console. About the Benchmark ABOUT TPC-C TPC-C is a data warehousing online transaction processing benchmark created by the Transaction Processing Council (TPC) and uses application databases such as Microsoft SQL Server. This benchmark is designed to simulate transactional requirements when a wholesale supplier processes orders. The “company” simulated by TPC-C consists of a number of geographically distributed sales districts serviced by associated warehouses. The TPC-C benchmark is composed of five transactions: 1) new order, 2) payment, 3) order status, 4) delivery and 5) stock level. Throughput is reported as tpmC (transaction per minute). You can find more information about this benchmark at http://www.tpc.org. ABOUT SQLIO (WITH PERMISSION FROM MICROSOFT) SQLIO is an I/O subsystem benchmark tool available from the Microsoft TPC-C kit. This benchmark performs basic I/O operations such as sequential or random reads and writes in various modes — direct and buffered. Users can also specify other parameters, such as block sizes, number of threads and maximum file sizes. Test Configurations TPC-C USING MICROSOFT SQL SERVER 2000 The test used a 500 warehouse TPC-C database for measurement. The test ran on a Dell 6300 quad Pentium II 550 MHz CPU, 1 GB RAM, three internal disks and 36 external disks. The internal disks consist of one 9 GB disk and two 18 GB disks. The external disks consist of three HP Rack Storage RS/12 dual SCSI channel disk arrays. Each disk array contains 12 disks. Software RAID is provided with three Brand Y cards. Two different hardware RAID controllers were used. The first hardware RAID controller is a high-end Brand X with 32 MB cache. The second hardware RAID controller is a midrange Brand Y with 32MB cache.


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http://www.tpc.org/

The Brand X RAID controller can have maximum 8 logical volumes with maximum 16 physical disks per logical volume. DISK I/O SUBSYSTEM TEST USING SQLIO The same hardware used in the TPC-C test machine was used for testing disk I/O subsystem using SQLIO. A 10 GB raw partition (i.e., no file system) was used. For direct random reads and random writes, the parameter used consisted of 2K, 8K, 64K and 128K block sizes and 1, 8, 32 and 128 threads on a 4 GB raw file size. Results RAID 0 TPC-C VM VS. BRAND X RAID CARD When running TPC-C with Microsoft SQL Server 2000, Volume Manager (VM) RAID 0 shows performance comparable to that of the Brand X card with write policy set to either write through or write back. On a 1-CPU-server machine (Figure 1), software RAID 0, hardware RAID 0 with write through, and hardware RAID 0 with write back shows comparable TPC-C throughput. Where the system is at 99 percent CPU use, hardware does better than software because striping a volume is offloaded to the hardware.

Figure 1: RAID 0 – VM vs. Hardware TPC-C (1 CPU, Brand X RAID)

Looking at the TPC-C throughput per minute (tpmC) results, VM shows 4,500 tpmC at 97 percent CPU use. At the same 4,500 tpmC throughput level for hardware RAID, the CPU use is at 93 percent. This suggests a 6 percent CPU overhead for using software striping three volumes in a one-way system as opposed to JBOD volumes. Another performance metric is to look at the overall efficiency as defined by the given throughput per unit CPU (tpmC/%CPU). At low workload, Volume Manager efficiency is 38 tpmC/CPU and hardware RAID 0 efficiency is 48 tpmC/CPU (i.e., hardware RAID 0 is 26 percent more efficient than software RAID 0). At high workload, Volume Manager efficiency is 46 tmpC/CPU and hardware RAID 0 efficiency is 50 tpmC/CPU (i.e., hardware RAID 0 is 9 percent more efficient than software RAID 0). This shows that on a CPU-constrained system, Volume Manager is less efficient than hardware RAID 0 because of the cost of doing software striping. On a 4-CPU system where CPU is not the bottleneck (Figure 2), Volume Manager shows higher throughput and comparable response time to that of hardware RAID 0 at light workload. At high workload, software RAID 0 maximum throughput is


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about 4,900 tpmC compared to 5,100 tpmC with hardware RAID 0 (i.e., 4 percent less than that of hardware RAID 0); response time is slightly higher for hardware. At this point, the disk is the bottleneck.

Figure 2: RAID 0 – VM vs. Hardware TPC-C (4 CPU, Brand X RAID)

Looking at the efficiency of the system, hardware RAID 0 efficiency is comparable to or slightly better than software RAID 0. In other words, hardware RAID 0 is –1 percent to 6 percent more efficient than VM RAID 0. At 4,900 tpmC throughput level, software RAID 0 CPU use is 61 percent; hardware RAID 0 CPU use is 57 percent. This means that software striping of three volumes incurs 4 percent more CPU. So on a system with plenty of CPU, sparing 4 percent CPU for software striping work will provide comparable throughput and is more cost-effective than purchasing a hardware controller to offload striping. RAID 0 TPC-C VM VS. BRAND Y RAID CARD When using a midrange Brand Y RAID controller card under light workload conditions (Figure 3), software and hardware RAID 0 show comparable results. As the server reaches a high workload condition, software RAID 0 shows better throughput and faster response time.

Figure 3: RAID 0 – VM vs. Hardware TPC-C (Brand Y RAID)


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RAID 0 SQLIO VM VS. BRAND X RAID CARD Test results for random reads show comparable performance at 2K, 4K and 64K I/O block size, but at 128K I/O block size, software RAID 0 shows 15 percent better performance (Figure 4). On random writes, software RAID 0 with write through and small I/O size has similar throughput. An exception is hardware RAID 0 with write back. This is due to writing to the hardware RAID controller cache. At large I/O block size, hardware RAID is slower than software RAID between 7 percent and 20 percent (Figure 5).

Figure 4: RAID 0 – Random Reads

In the case of hardware RAID implementation, the RAID controller manages the RAID volume and then exports it as a large physical disk volume to Volume Manager. So Volume Manager cannot take advantage of issuing concurrent I/O requests to each disk because from a Volume Manager standpoint, the logical volume contains only one physical disk.

Figure 5: RAID 0 – Random Writes

It is surprising to see that VM RAID 0 large I/O writes outperform hardware RAID 0. An explanation may be related to the number of disks per logical volume that are presented to Volume Manager. Volume Manager realizes a throughput advantage by issuing concurrent I/O requests to all the disks.


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In the case of hardware RAID implementation, the RAID controller manages the RAID volume and then exports it as a large physical disk volume to the Volume Manger. So Volume Manager cannot take advantage of issuing concurrent I/O requests to each disk because from a Volume Manager standpoint, the logical volume contains only one physical disk.

RAID 5 TPC-C VM VS. BRAND X RAID CARD In an environment where the server is not constrained by CPU, Volume Manager RAID 5 performance is comparable to that of the Brand X RAID controller card (Figure 6). On a 1-CPU system where the CPU is the bottleneck, hardware RAID 5 has 8 percent to 9 percent higher throughput and faster slower response time than Volume Manager RAID 5 as shown (Figure 7). Volume Manager RAID 5 peak TPC-C throughput is 2,200 tpmC at 97 percent CPU use. Hardware RAID 5 peak TPC-C throughput is 2,500–2,600 tpmC at 90 percent CPU use. The higher CPU usage is for software striping and parity calculation on a RAID 5 volume. In this case, where the CPU was at 97 percent busy, CPU becomes the constraining factor for delivering higher throughput.

Figure 6: RAID 5 – TPC-C with 1 and 4 CPU

Figure 7: RAID 5 – Volume Manager vs. Hardware TPC-C (1 CPU, High-End RAID)


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At the same 2,200 tpmC throughput level, Volume Manager RAID 5 CPU use is at 97 percent; hardware RAID 5 CPU use is at 80 percent. The efficiency of Volume Manager is 22.7 tpmC/CPU, and the efficiency of hardware RAID 5 is 28 tpmC/CPU. This suggests a 17 percent CPU overhead for using Volume Manager striping with parity on three volumes in a one-way system as opposed to JBOD volumes. Upon moving to a 4-CPU system where CPU is not the bottleneck, Volume Manager RAID 5 shows throughput comparable to that of the Brand X hardware RAID controller (Figure 8). As the load is increased past 2,400 tpmC, the disk becomes the bottleneck. At this point, Volume Manager RAID 5 peak throughput is 2,450 tpmC and hardware RAID 5 peak throughput is 2,600 tpmC — about a 6 percent difference.

Figure 8: RAID 5 – VM vs. Hardware TPC-C (4 CPU, High-End RAID)

At 2,400 tpmC throughput level, Volume Manager RAID 5 CPU use is 42 percent; hardware RAID 5 CPU use is 33 percent. This means that Volume Manager striping and parity calculations incurs 9 percent more CPU use. Looking at Volume Manager RAID 5, we observed an unexplained behavior. Running at 40 users (i.e., workload generators) with zero think time, the server under test delivers 2,400 tpmC at 42 percent CPU use. As the workload generator is increased to 120 users and the disk becomes the bottleneck, the throughput is 2,450 tpmC at 97 percent CPU use. This is not observed with the hardware RAID configuration. RAID 5 TPC-C VM VS. BRAND Y RAID CARD When using a midrange Brand Y RAID controller card, Volume Manger RAID 5 is much better than hardware RAID as shown (Figure 9). An interesting note is that within the hardware RAID 5 environment, configuring the RAID card writes policy to write through is better than configuring it to write back.


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Figure 9: RAID 5 – VM vs. Hardware TPC-C (Midrange RAID)

RAID 5 SQLIO VM VS. BRAND X RAID CARD Test results for random reads show comparable performance at 2K, 4K and 64K I/O block size, but at 128K I/O block size, Volume Manager RAID 5 shows 3 percent better performance (Figure 10). On random writes, Volume Manager RAID 5 with write through and small I/O size has similar throughput. An exception is hardware RAID 5 with write back. This is due to writing to the hardware RAID controller cache. At large I/O block size, hardware RAID is slower than Volume Manager RAID between 22 percent and 38 percent (Figure 11).

Figure 10: RAID 5 – Random Reads


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Figure 11: RAID 5 – Random Writes

It is surprising to see that Volume Manager RAID 5 writes outperform hardware RAID 5. An explanation may be related to the number of disks per logical volume that are presented to Volume Manager. The more physical disks per logical volume Volume Manager sees, the better Volume Manager can take advantage of issuing concurrent I/O requests to all the disks. In the case of hardware RAID implementation, the RAID controller manages the RAID volume and then exports it as a large physical disk volume to the Volume Manger. So Volume Manager cannot take advantage of issuing concurrent I/O requests to each disk because from a Volume Manager standpoint, the logical volume contains only one physical disk.


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Conclusion VERITAS Volume Manager for Windows 2000 (Volume Manager) software RAID 0 and RAID 5 perform comparably to the hardware RAID controller in database environments when CPU and disk are not the bottleneck. On a moderately loaded system (CPU ~50), using Volume Manager for RAID implementation offers comparable performance with substantial cost saving and flexible disk layout. Using Volume Manager for striping volumes (RAID 0) incurs 4 percent more CPU than using hardware RAID at 4,500 tpmC throughput level. Using Volume Manager for striping with parity volumes (RAID 5) incurs 9 percent more CPU than using hardware RAID at 2,200 tpmC throughput level.


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Appendix A: Database Layout


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Appendix B; Database Layout


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Appendix C: TPC-C Data for Midrange RAID Card


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Appendix D: SQLIO Data on High-End RAID


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For additional information about VERITAS Software, its products, or the location of an office near you, please call our corporate headquarters or visit our Web site at www.veritas.com.


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VERITAS VOLUME MANAGER™ FOR WINDOWS …eval.symantec.com/mktginfo/products/White_Papers/Storage_Server... · WHITE PAPER VERITAS Volume Manager™ for Windows 2000 VERITAS VOLUME