ivoras at fer.hr
Tue Nov 1 03:13:08 PST 2005
On Tue, 1 Nov 2005, Bruce Evans wrote:
> On Mon, 31 Oct 2005, Ivan Voras wrote:
>> I did this but e2fsck doesn't set the flag. Fortunately, I found out that
>> e2fsprogs includes "debugfs" utility with which I manually set the flag.
> Does e2fsck report the problem?
Surprisingly, no. It run normally (as far as I can tell) without reporting
anything. This was on an unmounted system that contained one large (3GB)
file created (actually extended from a 2G file) in the Windows ext2
driver, which also didn't set the flag (though its documentation said it
would). Maybe there's undocumented "features" regarding extending already
> Strangely enough, I first got interested in ext2fs under FreeBSD because
> testing showed that it was faster than ffs in one configuration, and this
> turned out to be mostly because of fragmentation:
Very nice explanation, thanks!
> - ext2fs under FreeBSD has a primitive block allocator that will give lots
> and never delete files, the layout is almost optimal. In particular,
> the layout is good after copying a large directory tree to a new file
This is what I was doing with msdosfs, and accidentally looked at the
defragmenter - the display was like it's been randomly fragmented. Now I
know why :)
> first few cylinder groups full and the rest unused, where Linux would
> use all the groups fairly evenly.
Not so good. I suppose this is not easaly fixable?
> - soft updates (in this test) is now not much faster than ordinary
> (-nosync -noasync) mounts and is much slower than async mounts. It
> used to be only 1.5 times slower than async mounts. This test was
I've noticed this too.
> - ext2fs is about twice as slow as the other 2 (worse for non-async writes).
> It is mostly because the block size is very small, and although this
> only necessarily costs extra CPU to do clustering, FreeBSD is optimized
> for ffs's default block size and does pessimal things with ext2fs's
> smaller sizes.
These effects are also very noticable with NTFS (default block size=4096
for all/most partition sizes) and FAT32 on smaller drives (where bs=4096 fits
FAT in 8MB).
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