XFS is a high performance journaling filesystem which originated on the SGI IRIX platform. It is completely multi-threaded, can support large files and large filesystems, extended attributes, variable block sizes, is extent based, and makes extensive use of Btrees (directories, extents, free space) to aid both performance and scalability. Refer to the documentation at <http://oss.sgi.com/projects/xfs/> for complete details. This implementation is on-disk compatible with the IRIX version of XFS. To compile this file system support as a module, choose M here: the module will be called xfs. Be aware, however, that if the file system of your root partition is compiled as a module, you'll need to use an initial ramdisk (initrd) to boot.
If you say Y here, you will be able to set limits for disk usage on a per user and/or a per group basis under XFS. XFS considers quota information as filesystem metadata and uses journaling to provide a higher level guarantee of consistency. The on-disk data format for quota is also compatible with the IRIX version of XFS, allowing a filesystem to be migrated between Linux and IRIX without any need for conversion. If unsure, say N. More comprehensive documentation can be found in README.quota in the xfsprogs package. XFS quota can be used either with or without the generic quota support enabled (CONFIG_QUOTA) - they are completely independent subsystems.
POSIX Access Control Lists (ACLs) support permissions for users and groups beyond the owner/group/world scheme. To learn more about Access Control Lists, visit the POSIX ACLs for Linux website <http://acl.bestbits.at/>. If you don't know what Access Control Lists are, say N.
If you say Y here you will be able to mount and use XFS filesystems which contain a realtime subvolume. The realtime subvolume is a separate area of disk space where only file data is stored. It was originally designed to provide deterministic data rates suitable for media streaming applications, but is also useful as a generic mechanism for ensuring data and metadata/log I/Os are completely separated. Regular file I/Os are isolated to a separate device from all other requests, and this can be done quite transparently to applications via the inherit-realtime directory inode flag. See the xfs man page in section 5 for additional information. If unsure, say N.
Say Y here to get an XFS build with many debugging features, including ASSERT checks, function wrappers around macros, and extra sanity-checking functions in various code paths. Note that the resulting code will be HUGE and SLOW, and probably not useful unless you are debugging a particular problem. Say N unless you are an XFS developer, or you play one on TV.