[Lustre-discuss] cleaning up on lustre

[Kalpak Shah]

On Tue, 2008-07-08 at 15:54 +0200, Papp Tamás wrote:
> Kalpak Shah wrote:
> > Doing a "lctl --device OSC_UUID deactivate" on the MDS will only stop
> > new objects from being allocated on that OST. To completely remove the
> > OST you need to use "lctl conf_param lustre-OST0000.osc.active=0". If
> >   
> What's the difference between lctl deactivate and 'completely remove', 
> is it permanent?

"lctl deactivate" on the _MDS_ means that MDS will not allocate new
objects on that OST.

If you do "lctl deactivate" on the clients then they will return -EIO
when accessing objects on this OST instead of waiting for recovery.

When you do "lctl conf_param lustre-OST0000.osc.active=0" this means
that when clients are mounted they will set the import related to that
OST as inactive thereby not waiting for recovery from that OST. You may
choose to use the physical volume for that OST for other purposes. Or
you can again activate it using "lctl conf_param
lustre-OST0000.osc.active=1".

> 
> 
> What does happen, if I deactivate an OST on the client, connect another 
> new one, create the same object ( from example a file, called test.txt 
> in the same directory), then recover the old OST again?
> 

When you add a new OST, it would get a new index (unless you set the
--index property in mkfs.lustre) and hence there should not be any
collision. Note that the entry in the MDS for test.txt will now point to
the new OST and not the old one. The object for test.txt on the old OST
will be a dangling object.

Thanks,
Kalpak

> Thank you,
> 
> tamas