5.1.2 About XFS Write Barriers

A write barrier assures file system consistency on storage hardware that supports flushing of in-memory data to the underlying device. This ability is particularly important for write operations to an XFS journal that is held on a device with a volatile write-back cache.

By default, an XFS file system is mounted with a write barrier. If you create an XFS file system on a LUN that has a battery-backed, non-volatile cache, using a write barrier degrades I/O performance by requiring data to be flushed more often than necessary. In such cases, you can remove the write barrier by mounting the file system with the -o nobarrier option to the mount command.