Comment 57 for bug 131094

Martin,

Actually I have done some more testing and discovered that when index merging no physical reads were done (they are all cache hits) so ext3 problem is handling a ton of small writes which it does very badly according to google (it fragments destroying performance and preventing contiguous writing to the index)

XFS in contrast does these very well with a lot of contiguous writing which results in almost no loss of speed thanks to its delayed allocation feature (http://en.wikipedia.org/wiki/Delayed_allocation) which tracker benefits from.

the good news is that this feature is under consideration for ext4 - https://ols2006.108.redhat.com/2007/Reprints/sato-Reprint.pdf

so fingers crossed!