[ale] Ubuntu Linux Defrag EXT4

[Greg Freemyer]

On Mon, Sep 13, 2010 at 11:58 AM, Ron Frazier
<atllinuxenthinfo at c3energy.com> wrote:
> Greg,
>
> Thanks for the tip.  Based on other comments, I don't think I'll be
> defragging Linux just yet.
>
> A few people mentioned corrupting a Linux / Unix HDD by running utilities
> while the partition is mounted.  When I run chkdisk on my Windows system in
> read / write mode, it pops up a dialog that says it can't run the test now
> because the system is in use.  It offers an option to run the test the next
> time I reboot, and I click yes or no.  Linux should offer me the same
> courtesy, in my opinion.
>
> Ron

e4defrag is designed to be used online (ie. with the FS mounted)

I'm not sure I was clear before, but I monitor the ext4 mailinglist
and have not seen a complaint of e4defrag causing data corruption in
over a year (maybe 2.6.32 timeframe).  All reported bugs have been
addressed and I believe backported to at least 2.6.32.

OTOH, Ted T'so (the ext4 maintainer) has said he would like to see a
more sophisticated test suite written for e4defrag to make sure it is
not causing any data corruption even in unusual filesystem configs.

ie. Various page sizes;  FS created as ext4;  FS converted from ext3
to ext4; with and without journaling; FS bigger than 16 TB.

So if you have a vanilla ext4 setup, you should be fine to run it
online.  If you have something more exotic like ext4 without a
journal, then I would personally be very hesitant.

Greg