[Lustre-discuss] completely emptying an OST

Brian J. Murrell brian.murrell at oracle.com
Sun Oct 24 18:21:51 PDT 2010


On Sun, 2010-10-24 at 15:48 -0400, Bob Ball wrote:
> We may need to completely empty an OST, so that we can more efficiently 
> format the underlying RAID-6 array (in light of recent discussions about 
> the stripe on this list).  What is the most efficient way to do this?  I 
> can use multiple clients running lfs_migrate from pre-prepared lists, 
> but that will likely be a relatively slow process.  Are there other, 
> perhaps better ways to do this?

If you have enough free space to duplicate the OST you could do a
byte-level copy of it, bringing it up on a completely new device.

But if you don't have that space available, lfs_migrate is about your
best choice.  Even with the excellent lfs_migrate script I would
strongly advise you be familiar with what lfs_migrate is doing and the
general process of object migration and at every step, "measure twice,
cut once".

When I do things like this, I typically spend many times as much time
verifying that my previous step was successful and what my next step
will be than I spend actually doing the steps.

Probably, similarly to how you describe using lists of objects on
multiple clients, lfs_migrate could be made to scale by using multiple
co-ordinated clients.  We always gladly accept patches.  :-)

Cheers,
b.





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