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StorNext
File System Tuning Guide File System Tuning Guide File System Tuning Guide
®
StorNext 3.5.2
6-01376-14
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StorNext 3.5.2 File System Tuning Guide, 6-01376-14, Ver. A, Rel. 3.5.2, February 2010, Made in USA. Quantum Corporation provides this publication “as is” without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability or fitness for a particular purpose. Quantum Corporation may revise this publication from time to time without notice. COPYRIGHT STATEMENT © Copyright 2000 - 2010 Quantum Corporation. All rights reserved. US Patent
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Contents Chapter 0 StorNext File System Tuning 1 The Underlying Storage System ...................................................................... 1 RAID Cache Configuration....................................................................... 2 RAID Write-Back Caching ........................................................................ 2 RAID Read-Ahead Caching ...................................................................... 3 RAID Level, Segment Size, and Stripe Size ............
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0StorNext File System Tuning The StorNext File System (SNFS) provides extremely high performance for widely varying scenarios. Many factors determine the level of performance you will realize. In particular, the performance characteristics of the underlying storage system are the most critical factors. However, other components such as the Metadata Network and MDC systems also have a significant effect on performance. Furthermore, file size mix and application I/O characteristics may also
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StorNext File System Tuning The Underlying Storage System RAID Cache The single most important RAID tuning component is the cache Configuration 0 configuration. This is particularly true for small I/O operations. Contemporary RAID systems such as the EMC CX series and the various Engenio systems provide excellent small I/O performance with properly tuned caching. So, for the best general purpose performance characteristics, it is crucial to utilize the RAID system caching as fully as po
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StorNext File System Tuning The Underlying Storage System operations involve a very high rate of small writes to the metadata disk, so disk latency is the critical performance factor. Write-back caching can be an effective approach to minimizing I/O latency and optimizing metadata operations throughput. This is easily observed in the hourly File System Manager (FSM) statistics reports in the cvlog file. For example, here is a message line from the cvlog file: PIO HiPriWr SUMMARY SnmsMetaD
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StorNext File System Tuning The Underlying Storage System While read-ahead caching improves sequential read performance, it does not help highly transactional performance. Furthermore, some SNFS customers actually observe maximum large sequential read throughput by disabling caching. While disabling read-ahead is beneficial in these unusual cases, it severely degrades typical scenarios. Therefore, it is unsuitable for most environments. RAID Level, Segment Configuration settings such as
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StorNext File System Tuning File Size Mix and Application I/O Characteristics example, varying the stripe size and running lmdd with a range of I/O sizes might be useful to determine an optimal stripe size multiple to configure the SNFS StripeBreadth. Some storage vendors now provide RAID6 capability for improved reliability over RAID5. This may be particularly valuable for SATA disks where bit error rates can lead to disk problems. However, RAID6 typically incurs a performance penalty co
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StorNext File System Tuning File Size Mix and Application I/O Characteristics Reads and writes that aren't well-formed utilize the SNFS buffer cache. Buffer Cache 0 This also includes NFS or CIFS-based traffic because the NFS and CIFS daemons defeat well-formed I/Os issued by the application. There are several configuration parameters that affect buffer cache performance. The most critical is the RAID cache configuration because buffered I/O is usually smaller than the RAID stripe size, a
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StorNext File System Tuning SNFS and Virus Checking It can be useful to use a tool such as netperf to help verify network performance characteristics. SNFS and Virus Checking Virus-checking software can severely degrade the performance of any file system, including SNFS. If you have anti-virus software running on a Windows Server 2003 or Windows XP machine, Quantum recommends configuring the software so that it does NOT check SNFS. The Metadata Network As with any client/server protocol
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StorNext File System Tuning The Metadata Controller System It can be useful to use a tool like netperf to help verify the Metadata Network performance characteristics. For example, if netperf -t TCP_RR reports less than 15,000 transactions per second capacity, a performance penalty may be incurred. You can also use the netstat tool to identify tcp retransmissions impacting performance. The cvadmin “latency-test” tool is also useful for measuring network latency. Note the following configu
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StorNext File System Tuning The Metadata Controller System However, it is critical that the MDC system have enough physical memory available to ensure that the FSM process doesn’t get swapped out. Otherwise, severe performance degradation and system instability can result. The operating system on the metadata controller must always be run in U.S. English. FSM Configuration File The following FSM configuration file settings are explained in greater Settings 0 detail in the cvfs_config man
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StorNext File System Tuning The Metadata Controller System MultiPathMethod Rotate Node CvfsDisk6 0 Node CvfsDisk7 1 [StripeGroup MetaFiles] Status UP MetaData Yes Journal No Exclusive Yes Read Enabled Write Enabled StripeBreadth 256K MultiPathMethod Rotate Node CvfsDisk0 0 [StripeGroup JournFiles] Status UP Journal Yes MetaData No Exclusive Yes Read Enabled Write Enabled StripeBreadth 256K MultiPathMethod Rotate Node CvfsDisk1 0 Affinities 0 Affinities are another st
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StorNext File System Tuning The Metadata Controller System For optimal performance, files that are accessed using large DMA-based I/O could be steered to wide-stripe stripe groups. Less performance- critical files could be steered to slow disk stripe groups. Small files could be steered to narrow-stripe stripe groups. Example: [stripeGroup AudioFiles] Status UP Exclusive Yes ##These two lines set Exclusive stripeGroup ## Affinity AudFiles ##for Audio Files Only## Read Enabled
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StorNext File System Tuning The Metadata Controller System Example: [stripeGroup VideoFiles] Status UP Exclusive Yes ##These Two lines set Exclusive stripeGroup## Affinity VidFiles ##for Video Files Only## Read Enabled Write Enabled StripeBreadth 4M MultiPathMethod Rotate Node CvfsDisk2 0 Node CvfsDisk3 1 BufferCacheSize 0 This setting consumes up to 2X bytes of memory times the number specified. Increasing this value can reduce latency of any metadata operation by performi
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StorNext File System Tuning The Metadata Controller System ThreadPoolSize 0 This setting consumes up to 512 KB memory times the number specified. Increasing this value can improve concurrency of metadata operations. For example, if many client processes are executing concurrently, the thread pool can become exhausted by I/O wait time. Increasing the thread pool size permits hot cache operations to be processed that would otherwise be backed up behind the I/O-bound operations. There are v
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StorNext File System Tuning The Metadata Controller System Note: This is particularly true for slow CPU clock speed metadata servers such as Sparc. However, values greater than 16K can severely consume metadata space in cases where the file-to- directory ratio is low (e.g. less than 100 to 1). For metadata disk size, you must have a minimum of 25 GB, with more space allocated depending on the number of files per directory and the size of your file system. The following table shows suggest
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StorNext File System Tuning The Metadata Controller System JournalSize 0 The optimal settings for JournalSize are in the range between 16M and 64M, depending on the FsBlockSize. Avoid values greater than 64M due to potentially severe impacts on startup and failover times. Values at the higher end of the 16M-64M range may improve performance of metadata operations in some cases, although at the cost of slower startup and failover time. The following table shows recommended settings. Choos
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StorNext File System Tuning The Metadata Controller System The following items are a few things to watch out for: • A non-zero value for FSM wait SUMMARY journal waits indicates insufficient IOPS performance of the disks assigned to the metadata stripe group. This usually requires reducing the metadata I/O latency time by adjusting RAID cache settings or reducing bandwidth contention for the metadata LUN. Another possible solution is to add another metadata stripe group to the file system
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StorNext File System Tuning The Metadata Controller System 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 B
