Quantum 6-01376-05 manual StorNext File System Tuning Metadata Controller System

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StorNext File System Tuning

The Metadata Controller System

• Zr: Hole in file was zeroed

Both traces also report file offset, I/O size, latency (mics), and inode number.

Sample use cases:

Verify that I/O properties are as expected.

You can use the VFS trace to ensure that the displayed properties are consistent with expectations, such as being well formed; buffered versus DMA; shared/non-shared; or I/O size. If a small I/O is being performed DMA, performance will be poor. If DMA I/O is not well formed, it requires an extra data copy and may even be broken into small chunks. Zeroing holes in files has a performance impact.

Determine if metadata operations are impacting performance.

If VFS throughput is inconsistent or significantly less than Device throughput, it might be caused by metadata operations. In that case, it would be useful to display “fsmtoken,” “fsmvnops,” and “fsmdmig” traces in addition to “perf.”

Identify disk performance issues.

If Device throughput is inconsistent or less than expected, it might indicate a slow disk in a stripe group, or that RAID tuning is necessary.

Identify file fragmentation.

If the extent count “exts” is high, it might indicate a fragmentation problem.This causes the device I/Os to be broken into smaller chunks, which can significantly impact throughput.

Identify read/modify/write condition.

If buffered VFS writes are causing Device reads, it might be beneficial to match I/O request size to a multiple of the “cachebufsize” (default 64KB; see mount_cvfs man page). Another way to avoid this is by truncating the file before writing.

The cvadmin command includes a latency-testutility for measuring the latency between an FSM and one or more SNFS clients. This utility causes small messages to be exchanged between the FSM and clients as quickly as possible for a brief period of time, and reports the average time it took for each message to receive a response.

StorNext File System Tuning Guide

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Contents 01376-05 Copyright Statement Contents StorNext File System Tuning Underlying Storage SystemRAID Cache Configuration RAID Write-Back Caching RAID Read-Ahead Caching RAID Level, Segment Size, and Stripe Size File Size Mix and Application I/O Characteristics Direct Memory Access DMA I/O TransferBuffer Cache NFS / Cifs Metadata Network Metadata Controller SystemFSM Configuration File Settings Stripe GroupsExample AffinitiesStripeBreadth BufferCacheSizeForcestripeAlignment InodeCacheSizeThreadPoolSize FsBlockSizeJournalSize Snfs ToolsStorNext File System Tuning Metadata Controller System StorNext File System Tuning Metadata Controller System StorNext File System Tuning Metadata Controller System MountCommandOptions StorNext File System Tuning Metadata Controller System Hardware Configuration Distributed LAN Disk Proxy NetworksSnfs External API StorNext File System Tuning Guide Network Configuration and Topology SAN Distributed LAN Servers Windows Memory RequirementsStorNext File System Tuning Windows Memory Requirements StorNext File System Tuning Windows Memory Requirements Sample FSM Configuration File MAXStripeBreadth StorNext File System Tuning Sample FSM Configuration File StorNext File System Tuning Sample FSM Configuration File StorNext File System Tuning Sample FSM Configuration File