Quantum 6-01376-07 manual StorNext File System Tuning Metadata Controller System

StorNext File System Tuning

The Metadata Controller System

SNFS supports the Windows Perfmon utility. This provides many useful statistics counters for the SNFS client component. To install, obtain a copy of cvfsperf.dll from the SCM team in Denver and copy it into the c:/ winnt/system32 directory on the SNFS client system. Then run rmperfreg.exe and instperfreg.exe to set up the required registry settings. After these steps, the SNFS counters should be visible to the Windows Perfmon utility. If not, check the Windows Application Event log for errors.

The cvcp utility is a higher performance alternative to commands such as cp and tar. The cvcp utility achieves high performance by using threads, large I/O buffers, preallocation, stripe alignment, DMA I/O transfer, and Bulk Create. Also, the cvcp utility uses the SNFS External API for preallocation and stripe alignment. In the directory-to-directory copy mode (for example, cvcp source_dir destination_dir,) cvcp conditionally uses the Bulk Create API to provide a dramatic small file copy performance boost. However, it will not use Bulk Create in some scenarios, such as non-root invocation, managed file systems, quotas, or Windows security. Hopefully, these limitations will be removed in a future release. When Bulk Create is utilized, it significantly boosts performance by reducing the number of metadata operations issued. For example, up to 20 files can be created all with a single metadata operation. For more information, see the cvcp man page.

The cvmkfile utility provides a command line tool to utilize valuable SNFS performance features. These features include preallocation, stripe alignment, and affinities. See the cvmkfile man page.

The Lmdd utility is very useful to measure raw LUN performance as well as varied I/O transfer sizes.

The cvdbset utility has a special “Perf” trace flag that is very useful to analyze I/O performance. For example: cvdbset perf

Then, you can use cvdb -gto collect trace information such as this:

PERF: Device Write 41 MB/s IOs 2 exts 1 offs 0x0 len 0x400000 mics 95589 ino 0x5

PERF: VFS Write EofDmaAlgn 41 MB/s offs 0x0 len 0x400000 mics 95618 ino 0x5

The “PERF: Device” trace shows throughput measured for the device I/ O. It also shows the number of I/Os into which it was broken, and the number of extents (sequence of consecutive filesystem blocks).