Re: [gentoo-user] aligning SSD partitions

[Paul Hartman]

On Wed, Sep 5, 2012 at 3:46 PM, Dale <rdalek1967@×××××.com> wrote:
> Paul Hartman wrote:
>> On Wed, Sep 5, 2012 at 1:02 PM, Dale <rdalek1967@×××××.com> wrote:
>>>
>>> I have to say that here, it is not a whole lot of fragmentation but it
>>> does seem a bit faster afterwards.  I guess it depends on what is
>>> fragmented and such.  I sometimes wonder if it defrags itself.  Even
>>> when I watch the fsck when booting, all the ext4 partitions have a very
>>> small percentage of fragmentation.  My /boot which is ext2 is fragmented
>>> as heck.  lol  I'm not worried about it tho.  ;-)  When I was using
>>> reiserfs, it was always a good bit of fragmentation.
>>>
>>> Just thought it was worth a mention since this is the first time I saw a
>>> Linux defrag tool.
>> I think almost all linux defrag tools/techniques deal with file
>> fragmentation only, that is to say one file with more than 1 extent,
>> but don't deal with filesystem fragmentation (10000 small files
>> scattered all over the drive, rather than written contiguously). So
>> I'm not surprised that Peter did not see fragmentation after
>> installing KDE.
>>
>> AFAIK almost all that modern defrag tools do is just copy the file,
>> allocating the whole file at once in the copy process, and if that new
>> copy has fewer extents than the old copy, it fills in the data, then
>> removes the original file. The concept is not entirely dissimilar to
>> the old "backup, format, restore" defrag process.
>>
>> Over the years I have used a poor-man's version of that concept to
>> defrag files. Just move it to another drive (or -- even better -- a
>> ramdrive/tmpfs), then move it back to disk (with a tool that performs
>> preallocation).
>>
>> There is a userland defrag tool that does exactly this, on any
>> filesystem. It is called "shake".
>>
>> Typically I only see fragmentation on large files that were copied
>> from a slow source (over the network/internet), or bittorrent clients
>> that do not preallocate space, etc. Any kind of streaming file that
>> was written, huge multi-gigabyte video recording files, that kind of
>> stuff. But the key to avoiding file fragmentation is preallocation...
>>
>>
>
> I used shake before but it just didn't seem to work right for me.  I
> found a script that does something and it seems to work for the most
> part but still not great or anything.  I just like the way ext4 works.
> Heck, I liked it before I found the defrag tool.  I've had this install
> for a while and it has never had much fragmentation even before the
> tool.  So, I find it funny that they make a tool that really isn't
> needed very much.  :/

I think shake's default options might require extended attributes
enabled in your mounted fs. It also has some thresholds for file size
and age that cause it to skip certain files, unless you tell it
otherwise. I haven't used it in quite a long time, to be honest. :)