Editing XFS (section)

===Snapshots===
XFS does not yet<ref>{{cite web|url=https://lwn.net/Articles/638546/|title=XFS: There and back ... and there again? [LWN.net]|website=lwn.net|access-date=2016-10-27|archive-url=https://web.archive.org/web/20161027192827/https://lwn.net/Articles/638546/|archive-date=2016-10-27|url-status=live}}</ref> provide direct support for snapshots, as it currently expects the snapshot process to be implemented by the volume manager. Taking a snapshot of an XFS filesystem involves temporarily halting I/O to the filesystem using the <code>xfs_freeze</code> utility, having the volume manager perform the actual snapshot, and then resuming I/O to continue with normal operations. The snapshot can then be mounted read-only for backup purposes.

Releases of XFS in IRIX incorporated an integrated volume manager called XLV. This volume manager has not been ported to Linux, and XFS works with standard [[Logical Volume Manager (Linux)|LVM]] in Linux systems instead.

In recent Linux kernels, the <code>xfs_freeze</code> functionality is implemented in the VFS layer, and is executed automatically when the Volume Manager's snapshot functionality is invoked. This was once a valuable advantage as the [[ext3]] file system could not be suspended<ref>{{cite web|url=http://www.linuxquestions.org/questions/programming-9/how-to-freeze-ext3-file-system-229937/|title=How to freeze ext3 file system|website=www.linuxquestions.org|access-date=2011-08-24|archive-url=https://web.archive.org/web/20110428190523/http://www.linuxquestions.org/questions/programming-9/how-to-freeze-ext3-file-system-229937/|archive-date=2011-04-28|url-status=live}}</ref> and the volume manager was unable to create a consistent "hot" snapshot to back up a heavily busy database.<ref>{{cite web|url=http://www.linuxquestions.org/questions/linux-server-73/lvm-snapshots-how-to-use-622084/|title=LVM snapshots: How to use?|website=www.linuxquestions.org|access-date=2010-04-17|archive-url=https://web.archive.org/web/20110117044017/http://www.linuxquestions.org/questions/linux-server-73/lvm-snapshots-how-to-use-622084/|archive-date=2011-01-17|url-status=live}}</ref> Fortunately this is no longer the case. Since Linux 2.6.29, the file systems ext3, [[ext4]], [[GFS2]] and [[JFS (file system)|JFS]] have the freeze feature as well.<ref>{{cite web|url=https://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c4be0c1dc4cdc37b175579be1460f15ac6495e9a|title=kernel/git/torvalds/linux.git - Linux kernel source tree|website=git.kernel.org}}</ref>