[Lustre-discuss] MDT backup procedure

[Jerome, Ron]

Hi John,

I migrated my MGS/MDT to new hardware just a few weeks ago without much
difficulty.  I did not use an LVM snapshots though, rather the procedure
outlined in the manual (section 15.1.3.1 of the 1.6 manual) using tar
(with the "sparse" option, this is very important!) and getattr.  Mine
is a combination MGS/MDT, so I also needed to tunefs.lustre --writeconf
to get the OST's to update their configuration logs on the new server.
I gave the new server the same IP address as the old one, so there
weren't any issues with changing nids.  It's been running great ever
since.

FYI, it took a few hours to create the tar and extended attribute files
on the old server (~3.4M inodes) and about half that time to restore
them onto the new server (faster disks :)  All in all, about 4 hours of
down time.

Ron Jerome
National Research Council Canada.

 
> -----Original Message-----
> From: lustre-discuss-bounces at lists.lustre.org [mailto:lustre-discuss-
> bounces at lists.lustre.org] On Behalf Of John White
> Sent: June 19, 2009 1:58 AM
> To: Adam Knight
> Cc: lustre-discuss at lists.lustre.org
> Subject: Re: [Lustre-discuss] MDT backup procedure
> 
> On Jun 17, 2009, at 4:09 PM, Adam Knight wrote:
> 
> > Pertaining to your original email, rather than taking the MDT down
to
> > backup, it is very convenient to use LVM snapshots.  With this
> > functionality it creates a LV duplicate of the MDT and allows you to
> > mount that as ldiskfs and backup files from a consistent copy (won't
> > be
> > changing even if your MDT continues to add/remove data).  Your
lustre
> > filesystem will therefore stay operational during the backup.  If
you
> > time it cleverly, you can snapshot your MDT and OSTs at the same
time
> > and backup from all of them to have a consistent copy of the whole
> > filesystem as well.
> >
> 
> So following this, has anyone migrated an MDT to new storage with this
> sort of procedure?
> 
> -create an lvm'd MDT that produces snapshots
> -use it for a while in production
> -get some snazzy new disk
> -shutdown lustre
> -take a snapshot of the MDT and shuffle it off to some different
> storage media
> -create a new LVM with snazzy new disk (specifically of a different
> size from the original MDT)
> -restore snapshot
> -run lfsck for good measure (is this advisable on what could feasibly
> be a clean filesystem?)
> -bring up lustre
> 
> Please keep in mind, I've used LVM but haven't used snapshots, I'm not
> familiar with their limitations.  We're looking to create a filesystem
> immediately but would like to get some much faster storage for the MDT
> later without burning and building a new FS.
> 
> >> Thanks for this verbose reply.  It is exactly what I needed and
> >> what I suspected I would run into.  We are planning on multiple
> >> backup procedures.  Users will backup at checkpoints in their work
> >> flow, IT will backup the MDT nightly and we are also looking at the
> >> possibility of backup the complete file system.
> >>
> >> Thanks again for everyone's input, this gives me some good
> >> ammunition going forward for proposals.
> >>
> >> Thanks,
> >>  Dan Kulinski
> >>
> >>
> >>
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