xfs_rtcp

xfs_rtcp [ -v ] infile outfile

-v
    Enables verbose output, displaying information about the allocation process, such as the extent information for the new file.

infile
    The path to the source file to be copied. This file can be from any filesystem type.

outfile
    The path to the destination file on the XFS filesystem's realtime section. This path must reside on an XFS filesystem that was created with a realtime section.

xfs_rtcp is a utility designed to copy files into the dedicated realtime section of an XFS filesystem. This section provides guaranteed I/O bandwidth, making it ideal for applications requiring consistent performance, such as multimedia streaming, video capture, or specialized databases. When a file is copied with xfs_rtcp, the command attempts to allocate it contiguously within the realtime section. If the file cannot be allocated contiguously or if the target filesystem does not have a realtime section, the command will fail.

This utility is crucial for workloads where predictable I/O latency and throughput are paramount, ensuring that the data is stored in a way that maximizes performance and minimizes fragmentation in a performance-critical area of the disk.

The target XFS filesystem must have been created with a realtime section (e.g., using mkfs.xfs -r options).
xfs_rtcp attempts to allocate the file contiguously within the realtime section. If a contiguous block of the required size is not available, the command will fail, even if non-contiguous space exists.
The file to be copied must fit entirely within the available space of the realtime section. If it exceeds the realtime section's capacity, the command will fail.

The realtime section in XFS is distinct from the regular data section. It's designed to provide 'guaranteed rate I/O' by pre-allocating disk space and attempting to maintain contiguity, which minimizes seek times and rotational latency, leading to more predictable performance. This is achieved by creating the filesystem with a separate device or a dedicated portion of a device specifically for the realtime section, isolated from general filesystem activity.

While xfs_rtcp attempts contiguous allocation, it does not reserve space or guarantee future success. If the realtime section becomes fragmented over time or if a sufficiently large contiguous block is unavailable at the time of copying, xfs_rtcp will fail to copy the file. Regular XFS fragmentation tools (like xfs_fsr) generally do not defragment the realtime section, as its purpose relies on initial contiguous allocation rather than post-creation defragmentation.

XFS was developed by Silicon Graphics (SGI) in the early 1990s, specifically for its IRIX operating system, to handle large filesystems and high I/O throughput for multimedia and graphics applications. The realtime section was a core feature from its inception, designed to meet the stringent performance demands of these applications by providing guaranteed bandwidth. XFS was later ported to Linux and became available in the kernel around 2001. The xfs_rtcp utility is part of the xfsprogs package, maintaining its original purpose of facilitating optimal storage for time-sensitive data on XFS filesystems with realtime capabilities. Its usage has continued in environments where predictable storage performance is critical, such as professional media production, high-performance computing, and specialized server applications.

mkfs.xfs(8), xfs(5), xfs_admin(8), xfs_info(8)