[Lustre-discuss] MDT backup procedure

[John White]

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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