Linux filesystems do indeed fragment albeit at a slower rate than NTFS.
No. I do not have hard statistics at hand but the Linux filesystems will fragment at a very similar rate as NTFS.
Depends on filesystem in question. ReiserFS fragments at crazy rate. Ext2, ext3 and ext4, on the other hand, fragment at somewhat slower rate than NTFS. How do I know? I did some tests (please see below). For example, my old laptop running Linux on ext3 filesystem has less than 1.05 average fragments per file.
There are reliable studies/experiments showing performance degradation from fragmentation on Windows, but there are no such studies for Linux (AFAIK).
There are no studies because Linux does not have tools to measure and correct the fragmentation. With all respect, but the absence of studies does not prove that there is no problem.[/quote]
There exists a tool that measures fragmentation on Linux. Please see the following thread in Gentoo forums for more detail: http://forums.gentoo.org/viewtopic-t-429915.html
. But I do agree with you that the absence of studies does not prove the absence of problems. The truth is that one cannot say anything definite about performance degradation due to fragmentation in Linux, unless someone did some thorough tests on this topic.
Also, the structure of Linux filesystems differs from that of NTFS, so defragmentation of Linux filesystems may give unexpected results such as a reduction in performance (due to e.g. the fact that related files are moved farther apart from each other during defrag).
The theoretical degradation that you describe also applies to NTFS, there is no magical difference in this respect. Also, the effect depends on the defragmentation program. Not on the filesystem.
I agree that many things depend the defrag program (are you referring to various file placement optimizations built into defrag programs?). But, IMHO, filesystem plays some role, too. E.g. xfs
deliberately 'fragments' data into several allocation groups, which may be very beneficial performance-wise when volume is filled by more than half.