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On Wed, Sep 5, 2012 at 1:02 PM, Dale <rdalek1967@×××××.com> wrote: |
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> Peter Humphrey wrote: |
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>> On Wednesday 05 September 2012 13:02:01 Dale wrote: |
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>> |
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>>> I find that after a big update, like KDE, it helps to defrag /usr. |
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>> Interesting. I've just run sudo e4defrag -c /usr and got a fragmentation |
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>> of zero. That's after upgrading KDE last week. |
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>> |
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>> Then I ran it on all the nine ext4 partitions here and only two had |
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>> nonzero fragmentations; one was 1 and the other 2. |
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>> |
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>> Looks like I can forget about it on this box. |
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>> |
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> |
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> I have to say that here, it is not a whole lot of fragmentation but it |
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> does seem a bit faster afterwards. I guess it depends on what is |
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> fragmented and such. I sometimes wonder if it defrags itself. Even |
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> when I watch the fsck when booting, all the ext4 partitions have a very |
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> small percentage of fragmentation. My /boot which is ext2 is fragmented |
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> as heck. lol I'm not worried about it tho. ;-) When I was using |
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> reiserfs, it was always a good bit of fragmentation. |
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> |
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> Just thought it was worth a mention since this is the first time I saw a |
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> Linux defrag tool. |
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|
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I think almost all linux defrag tools/techniques deal with file |
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fragmentation only, that is to say one file with more than 1 extent, |
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but don't deal with filesystem fragmentation (10000 small files |
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scattered all over the drive, rather than written contiguously). So |
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I'm not surprised that Peter did not see fragmentation after |
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installing KDE. |
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AFAIK almost all that modern defrag tools do is just copy the file, |
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allocating the whole file at once in the copy process, and if that new |
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copy has fewer extents than the old copy, it fills in the data, then |
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removes the original file. The concept is not entirely dissimilar to |
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the old "backup, format, restore" defrag process. |
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|
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Over the years I have used a poor-man's version of that concept to |
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defrag files. Just move it to another drive (or -- even better -- a |
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ramdrive/tmpfs), then move it back to disk (with a tool that performs |
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preallocation). |
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|
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There is a userland defrag tool that does exactly this, on any |
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filesystem. It is called "shake". |
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Typically I only see fragmentation on large files that were copied |
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from a slow source (over the network/internet), or bittorrent clients |
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that do not preallocate space, etc. Any kind of streaming file that |
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was written, huge multi-gigabyte video recording files, that kind of |
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stuff. But the key to avoiding file fragmentation is preallocation... |
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