Quantum 3.1.4.1 manual BufferCacheSize, InodeCacheSize, ThreadPoolSize

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StorNext File System Tuning

The Metadata Controller System

BufferCacheSize

This setting consumes up to 2X bytes of memory times the number specified. Increasing this value can reduce latency of any metadata operation by performing a hot cache access to directory blocks, inode information, and other metadata info. This is about 10 to 1000 times faster than I/O. It is especially important to increase this setting if metadata I/O latency is high, (for example, more than 2ms average latency). We recommend sizing this according to how much memory is available; more is better. Optimal settings for BufferCacheSize range from 16MB to 128MB.

Example: # BufferCacheSize

64M

# default 32MB

InodeCacheSize

This setting consumes about 800-1000 bytes of memory times the number specified. Increasing this value can reduce latency of any metadata operation by performing a hot cache access to inode information instead of an I/O to get inode info from disk, about 100 to 1000 times faster. It is especially important to increase this setting if metadata I/O latency is high, (for example, more than 2ms average latency). You should try to size this according to the sum number of working set files for all clients. Optimal settings for InodeCacheSize range from 16K to 128K.

Example: InodeCacheSize 16K # 1000-1200 bytes each, default 8K

ThreadPoolSize

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 various O/S limits to the number of threads that can cause fatal problems for the FSM daemon, so it's not a good idea to set this setting too high. A range from 32 to 128 is recommended, depending on the amount of available memory. It is recommended to size it according to the max threads FSM hourly statistic reported in the cvlog file. Optimal settings for ThreadPoolSize range from 32K to 128K.

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