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Re: How stable is ext3fs?



On Fri, Mar 01, 2002 at 02:15:24PM -0800, Andrew Morton wrote:
> 
> Mail produces "slow-growth" files.  Which means that their blocks
> are sprinkled all over the disk.   If you're adding a few k per hour to
> a file, the fs just about never manages to allocate the blocks
> contiguously.  A while back, I had a six-month-old multi-megabyte
> mailbox which had precisely *zero* contiguous blocks.  It was 100%
> fragmented!

Yeah, we really need to get preallocation working again for ext3, and
it would be useful if the filesystem could notice the mail case, and
to not release the preallocated blocks back to the system when the
file descriptor is closed.  

> For the above reasons, I partition my machines with all partitions
> the same size, and keep one free.  For the monthly theraputic
> copy-all-files-and-switch-mountpoints speedup.
> 
> It's all a bit sad, really.

Well, perhaps it time that someone rewrote the defragger to work with
4k blocks, and so that it doens't leave your filesystem a smoking heap
of debris if your system crashes in the middle of the defrag
operation.   :-) 

I haven't really noticed a major slowdown effect, but that's probably
because I was used to speed of using emacs RMAIL, and for large mail
files, mutt is blazingly fast in comparison, fragmented files or no.

As always, there's always more work to that we could do to make things
better, and not enough time to do it.  :-)

					- Ted





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