[lustre-discuss] OST -> MDT migration and MDT -> OST migration

[Bill Anderson]

    Thanks!



On Thu, Apr 15, 2021 at 1:08 AM Andreas Dilger <adilger at whamcloud.com>
wrote:

> On Apr 15, 2021, at 00:52, Åke Sandgren <ake.sandgren at hpc2n.umu.se> wrote:
> >
> > 
> >
> >> On 4/15/21 5:12 AM, Andreas Dilger via lustre-discuss wrote:
> >> On Apr 14, 2021, at 18:42, Bill Anderson via lustre-discuss
> >> <lustre-discuss at lists.lustre.org
> >> <mailto:lustre-discuss at lists.lustre.org>> wrote:
> >>>
> >>>
> >>>    Hi All,
> >>>
> >>>    I'm trying to figure out how to migrate files stored on an OST to
> >>> an MDT (that's using DoM) and to migrate files stored on an MDT to an
> >>> OST (e.g., if the MDT is getting full).  I can see how to migrate
> >>> between OSTs, but not between OSTs and MDTs.  I'm running Lustre
> 2.12.3.
> >>>
> >>>  Do you happen to know the syntax for migration between OSTs and MDTs?
> >>>
> >>>    Thanks for any help!
> >>
> >> You just use "lfs migrate <file layout> <file>" to migrate from DoM
> >> files to OST objects.  However, OST-to-DoM migration isn't available
> >> until 2.13.
> >
> > Couldn't you just use lfs mirror extend with a PFL that points into the
> > DoM, and then a resync/split
>
> Yes, and that's what happens in 2.13 when this functionality is
> implemented. To migrate from DoM->OST you can just make a copy of
> the file and swap layouts. The issue in 2.12 is that you can't write into
> the
> MDT inode to do OST->DoM migration/mirroring.
>
> Cheers, Andreas
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