Messages in this thread | | | Date | Tue, 8 Dec 1998 16:39:38 -0500 | Subject | Re: atomicity | From | tytso@mit ... |
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Date: Mon, 7 Dec 1998 02:42:05 -0800 (PST) From: Tracy R Reed <treed@ultraviolet.org>
> With ext2fs you should never need a defragmenter
What does this mean? Is 22.4 % insignificant or should I be worried?
/dev/md1: 2407/78624 files (22.4% non-contiguous), 185079/313260 blocks
A high non-contiguous percentage doesn't necessary mean that your filesystem is highly fragmented. Files which are larger than the maximum number of data blocks available in a block group are guaranteed to be non-contiguous, by the very nature of the ext2 filesystem.
Hence, I was very hesitant when I included that metric in e2fsck, since it could be very easily misused and misunderstood. The problem is that doing a better metric is rather difficult.
So for example, in the above example, there are 2407 files taking up 185 megabytes, for an average size of 77k a file. Given that there is usually a large number of small files (i.e., less than 10k), there is likely a goodly number of large files which are much more likely to overflow the confines of the block group and thus get counted as a "non-contiguous" file. But more simply, there's a big difference between a file which has the following allocation pattern:
Blocks 10-8191, 8202-6000
and ....
Blocks 10-20, 30-56, 60, 64-66, 100-140, 142-143, 150-200, ....
Both of the above two files are counted as a single "non-contiguous" file. But obviously, there's a very big difference as to the fragmentation of that particular file.
- Ted
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