StorNext File System Tuning
File Size Mix and Application I/O Characteristics
File Size Mix and Application I/O Characteristics
Direct Memory Access (DMA) I/O Transfer
It is always valuable to understand the file size mix of the target dataset as well as the application I/O characteristics. This includes the number of concurrent streams, proportion of read versus write streams, I/O size, sequential versus random, Network File System (NFS) or Common Internet File System (CIFS) access, and so on.
For example, if the dataset is dominated by small or large files, various settings can be optimized for the target size range.
Similarly, it might be beneficial to optimize for particular application I/O characteristics. For example, to optimize for sequential 1MB I/O size it would be beneficial to configure a stripe group with four 4+1 RAID5 LUNs with 256K stripe size.
However, optimizing for random I/O performance can incur a performance
Furthermore, NFS and CIFS access have special requirements to consider as described in the Direct Memory Access (DMA) I/O Transfer section.
To achieve the highest possible large sequential I/O transfer throughput, SNFS provides
| Reads and writes that aren't | |
Buffer Cache | ||
This also includes NFS or | ||
| ||
| daemons defeat | |
| 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, and therefore | |
| incurs a read/modify/write penalty. It might also be possible to match | |
| the RAID stripe size to the buffer cache I/O size. However, kernel | |
| memory fragmentation can defeat attempts to increase the SNFS buffer | |
| cache I/O size (see the cachebufsize setting described in the Mount |
StorNext File System Tuning Guide | 5 |