HP-UX 11i v3 Mass Storage I/O Performance Improvements

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HP-UX 11i v3

Mass Storage I/O Performance Improvements

Technical white paper

Table of contents

Introduction......................................................................................................................................... 2

Native multi-pathing............................................................................................................................. 2

Increased I/O throughput.................................................................................................................. 3

Decreased CPU utilization in cell-based systems................................................................................... 5

Boot and scan improvements................................................................................................................. 7

Crash dump performance improvements................................................................................................. 8

Improved performance tracking tools ..................................................................................................... 9

New SCSI tunables.............................................................................................................................. 9

LVM improvements............................................................................................................................. 10

Async Disk Driver Improvements .......................................................................................................... 11

Glossary........................................................................................................................................... 12

For more information.......................................................................................................................... 13

Send comments to HP......................................................................................................................... 13

Summary of content (13 pages)

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HP-UX 11i v3 Mass Storage I/O Performance Improvements Technical white paper Table of contents Introduction......................................................................................................................................... 2 Native multi-pathing ............................................................................................................................. 2 Increased I/O throughput...........................................................................................
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Introduction HP-UX 11i v3 introduces a new mass storage subsystem that provides improvements in manageability, availability, scalability, and performance.
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The load-balancing policies operate on the list of available paths to a LUN, which can change as paths go offline or online due to error conditions or by a user disabling paths with the scsimgr command. For more information, see scsimgr(1M) and The performance benefits of load-balancing include the following: • Increased I/O throughput through balanced utilization of all available paths.
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Figure 2 shows I/O throughput results on a system with a configuration similar to that in Figure 1, using legacy DSFs which are all associated with a single HBA port. On 11i v2, or with loadbalancing disabled, all the I/O goes through the one HBA port. On 11i v3, with load-balancing enabled, the I/O gets balanced automatically across paths through all four HBA ports, producing in this case about 3.6 times the throughput of the load-balancing disabled case.
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IOPS (IOs per second) Figure 3 I/Os per second (two paths per LUN) 350,000 2.02x 2.07x 300,000 11i v3 250,000 11i v3 200,000 150,000 100,000 50,000 0 11i v2 11i v2 Reads Writes HP-UX 11i v2 153,000 147,000 HP-UX 11i v3 309,000 305,000 I/Os performed on a set of legacy DSFs, all through a single HBA port. I/Os performed on the same set of legacy DSFs. Native Multi-Pathing automatically takes advantage of paths through both HBA ports.
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is also due to better cache-locality algorithms in the new mass storage stack and the rest of the HP-UX 11i v3 kernel. The cell-local round robin policy requires at least one LUN path per cell for optimal performance. When this requirement is met, the cell-local round-robin can significantly improves the overall I/O performance while decreasing the CPU overhead and scaling well with the number of cells. Figure 4 I/Os per second, 8 paths/LUN, Cell-Local Round-robin 500,000 200% 450,000 180% 2.
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The cell-local round robin scheduling policy is beneficial in those cell based system configurations where cell local memory is set up and a uniform distribution of interface cards across all the cells of the system exists. Boot and scan improvements The HP-UX 11i v3 mass storage stack fully parallelizes the probing of HBAs, targets, and LUNs to reduce I/O scan and system boot times.
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Figure 5 Boot and scan times 10.00 Elapsed Time (minutes) 9.00 1.4x 8.00 Improvement 7.00 6.00 5.00 4.00 3.00 2.00 4.6x 1.00 Improvement 0.00 Initial Scan During Boot Shutdown & Reboot Time HP-UX 11i v2 3.37 10.00 HP-UX 11i v3 0.73 (44 seconds) 7.00 Figure 6 Run-time ioscan times 20 18 Elapsed Time (seconds) 16 14 12 2x 10 8 6 3.7x 4 13x 2 0 'ioscan' 'ioscan -kf' 'ioscan -kfn' 'ioscan -kfnN' HP-UX 11i v2 19 12 16 0.0 n/a HP-UX 11i v3 9.5 0.9 4.3 2.
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Improved performance tracking tools The HP-UX 11i v3 mass storage stack provides new or improved performance tracking capabilities, including information regarding: • Per HBA port performance • Tape performance • Read/Write performance • Per lunpath performance • Statistics at various levels of the mass storage stack You can display the per HBA port performance data with the new –H option to the sar command, or with new options in the GlancePlus system performance monitor.
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• escsi_maxphys — The maximum I/O size allowed on the system. This tunable replaces the scsi_maxphys system tunable available on previous releases of HP-UX. The default setting is increased from 1 MB to 2 MB in HP-UX 11i v3, with corresponding interface driver enhancements to support the larger size. The Logical Volume Manager (LVM) is enhanced in HP-UX 11i v3 to support the larger I/O sizes, as discussed in LVM improvements. • max_q_depth — The maximum number of I/O requests outstanding per LUN path.
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• Native Multi-Pathing support. LVM is designed to work seamlessly with the native multi-pathing, enabling all of the corresponding performance benefits without having to be concerned with the specifics of LUN paths. • Fast vgscan. With the new -k option, vgscan can recover activated volume groups in /etc/lvmtab quickly (in seconds), even if the system has large number of LVM disks configured. • Striping + mirroring support. Previously a logical volume could be mirrored or striped but not both.
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Glossary Async Disk Driver The Asynchronous Disk Pseudo Driver in HP-UX, named asyncdsk in the OS, is used to perform asynchronous I/O in a user application for improved performance. User processes or threads in which asynchronous I/O is performed do not need to wait for the I/O to complete before going on to do other work. Instead they are asynchronously notified of I/O completions. The Async Disk Driver is commonly used with the Oracle database application on HP-UX.
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For more information http://www.hp.com/go/hpux11i To read more about the HP-UX, see the following: • Manpages (either installed on the system or at http://www.hp.com/go/hpux-clickable-manpages • HP-UX System Administration Guide: Security Management at: http://www.hp.com/go/hpux-core-docs Click on the HP-UX version you want and scroll down to User guide.