XFS: the filesystem of the future?

Posted Jan 24, 2012 0:41 UTC (Tue) by dlang (guest, #313)
In reply to: XFS: the filesystem of the future? by dgc
Parent article: XFS: the filesystem of the future?

> Inode numbers in XFS are an encoding of their location on disk. To shrink, you have to physically move inodes and so their number changes.

If I understand this correctly, this means that a defrag operation would have the same problems. Does this mean that there is no way (other than backup/restore) to defrag XFS?

as for the rest of the problems (involving moving metadata), would a data-only shrink that couldn't move metadata make any sense at all?

XFS: the filesystem of the future?

Posted Jan 24, 2012 2:04 UTC (Tue) by dgc (subscriber, #6611) [Link] (1 responses)

xfs_fsr doesn't change the inode number. It copies the data to another temporary file and if the source file hasn't changed once the copy is complete, it atomically swaps the extents between the two inodes via a special transaction. It uses invisible IO, so not even the timestamps on the inode being defragged get changed.

As to data only shrink, that makes no sense because metadata like directories will pin the blocks high up in the filesystem. and so you won't be able to shrink it anyway....

XFS: the filesystem of the future?

Posted Jan 24, 2012 8:13 UTC (Tue) by tialaramex (subscriber, #21167) [Link]

OK, so XFS doesn't support full defrag, it can't move metadata to improve performance - but it does have a data-only defrag which will be enough for some people.