XFS combines advanced journaling technology with full 64-bit addressing and scalable structures and algorithms. This combination delivers the most scalable and high-performance filesystem in the world.
The XFS Filesystem provides the following major features:
The XFS filesystem provides the advantages of journaling while minimizing the performance impact of journaling on read and write data transactions. Its journaling structures and algorithms are tuned to log the transactions rapidly.
XFS uses efficient table structures for fast searches and rapid space allocation. XFS continues to deliver rapid response times, even for directories with tens of thousands of entries.
XFS is a full 64-bit filesystem, and thus, as a filesystem, is capable of handling files as large as a million terabytes.
263 = 9 x 1018 = 9 exabytes
In future, as the filesystem size limitations of Linux are eliminated XFS will scale to the largest filesystems
A million terabytes is about a million times larger than most large filesystems in use today. This may seem to be an extremely large address space, but it is needed to plan for the exponential disk-density improvements observed in the disk industry in recent years. As the disk sizes grow, not only does the address space need to be sufficiently large, but the structures and algorithms need to scale. XFS is ready today with the technologies needed for this scalability.
XFS as a filesystem is capable of delivering near-raw I/O performance. XFS has proven scalability on SGI MIPS systems of multiple gigabytes/sec on multiple terabyte filesystems. As the bandwidth capabilities of Linux improve, the XFS filesystem will be able to utilize those capabilities.
Technology
Journaled 64-bit filesystem with guaranteed filesystem consistency.
Product Span
Available on Linux 2.4.
Quotas
The Linux XFS filesystem supports both user and group quotas.
Extended Attributes
XFS implements fully journaled extended attributes. An extended attribute is a name/value pair associated with a file. Attributes can be attached to all types of inodes: regular files, directories, symbolic links, device nodes, and so forth. Attribute values can contain upto 64KB of arbitrary binary data. XFS implements two attribute namespaces: a user namespace available to all users, protected by the normal file permissions; and a system namespace, accessible only to privileged users. The system namespace can be used for protected filesystem meta-data such as access control lists (ACLs) and hierarchical storage manager (HSM) file migration status.
POSIX Access Control Lists (ACLs)
The Linux XFS filesystem supports the ACL semantics and interfaces described in the draft POSIX 1003.1e standard.
Maximum File Size
For Linux 2.4, the maximum accessible file offset is 16TB on 4K page size and 64TB on 16K page size. As Linux moves to 64 bit on block devices layer, file size limit will increase to 9 million terabytes (or the system drive limits).
Maximum Filesystem Size
For Linux 2.4, 2 TB. As Linux moves to 64 bit on block devices layer, filesystem limits will increase.
Filesystem Block Size
Currently fixed at the system page size - 4K on IA32. Filesystem extents (contiguous data) are configurable at file creation time using fcntl and are multiples of the filesystem block size. Single extents can be up to 4 GB in size.
Physical Disk Sector Size Supported
512 bytes
NFS Compatibility
With NFS version 3, 64-bit filesystems can be exported to other systems that support the NFS V3 protocol. Systems that use NFS V2 protocol may access XFS filesystems within the 32-bit limit imposed by the protocol.
Windows NT Compatibility
SGI uses the Open Source Samba server to export XFS filesystems to Windows and Windows NT systems. Samba speaks the SMB (Server Message Block) and CIFS (Common Internet File System) protocols.
Backup/Restore
xfsdump and xfsrestore can be used for backup and restore of XFS file systems to local/remote SCSI tapes or files. It supports dumping of extended attributes and quota information. As the xfsdump format has been preserved on Linux, XFS dumps created on either IRIX or Linux can be restored onto an XFS filesystem on either operating system.
Support for Hierarchical Storage
The Data Management API (DMAPI/XDSM) allows implementation of hierarchical storage management software with no kernel modifications as well as high-performance dump programs without requiring "raw" access to the disk and knowledge of filesystem structures.
Swap to Files
Swap to files is supported.
Memory
64 MB recommended.