Vxfs file systems

This space cannot be allocated to other files in the file system. VxFS prevents any unexpected out-of-space condition on the file system by ensuring that a file's required space will be associated with the file before it is required. The block size can have major benefits and disadvantages. The number of inodes is a major factor in the runtime of a full fsck. Placing files in a single directory can impact performance:. Hundreds or even thousands of very large, pre-allocated files with contiguous extents are much easier to handle than hundreds of millions of medium sized files.

The maximum size of the file system you can create depends on the block size and is different for each platform. VxFS supports creating a 16PB file system on Linux with 8kB block size, however, due to practical reasons we would NOT normally recommend having a file system anywhere near this size.

The default block size is 1Kb for file system sizes of up to 2Tb, and 8Kb for file system sizes 2Tb or larger. You specify the block size when creating a file system by using the mkfs-o bsize option. The block size cannot be altered after the file system is created. Choose a block size based on the type of application being run.

For example, if there are many small files, a 1 KB block size may save space. For large file systems, with relatively few files, a larger block size is more appropriate. Larger block sizes use less disk space in file system overhead, but consume more space for files that are not a multiple of the block size.

The easiest way to judge which block sizes provide the greatest system efficiency is to try representative system loads against various sizes and pick the fastest.

However, for Linux starting from VxFS version 7. The entire file system space, starting at block 0, is divided into fixed size allocation units AU of 32, blocks 32k.

A major factor to consider the size of your file system, is the recovery of the file system in the event that an fsck or metasave needs to be actioned to repair a damaged file system.

The VxFS file system uses a full structural verification utility called fsck to recover a damaged file system following a system failure unplanned outage. This involves a time-consuming process of checking the entire file system structure, verifying that the file system is intact, and correcting any inconsistencies.

This feature records pending changes to the file system structure in a circular intent log. The mount command automatically runs the VxFS fsck command to perform an intent log replay if the mount command detects a dirty log in the file system.

The VxFS intent log is allocated when the file system is first created and the size is determined by the size of the file system. The improvement over log mode is typically about 15 to 20 percent with delaylog ; with tmplog , the improvement is even higher. Performance improvement varies, depending on the operations being performed and the workload. The best way to select a mode is to test representative system loads against the logging modes and compare the performance results.

Most of the modes can be used in combination. Problem VxFS file system is taking too much memory. This will take up some portion of memory not needed by VxFS and better utilized elsewhere. This should resolve the memory shortage problems, which are believed to be caused by VxFS. On the system side, the problem is not having a big enough dump device, and it can be resolved by limiting the size of the dump device or increasing the size of the dump device.

The following tunables areused:. Every entry in the disk has to point to an entry in the inode table. This value depends on:. To determine VxFS Kmemusage The sun4d architecture only supports up to M of kernel memory, which in this case would only leave 93M of kernel memory for other system kernel memory requests. One approach to rectify this situation would be to tune the VxFS variables such that it does not consume so much kernel memory. The amounts that these should be tuned are going to be highly dependent on your estimation of what constitutes an acceptable amount of kmem for VxFS to be using.

This would be associated with how many files are open in VxFS file systems at any given time.