Re: cephfs-fuse: set/getfattr, change pools

[Daniel Schneller <daniel.schneller@xxxxxxxxxxxxxxxx>]

Understood. Thanks for the details.

Daniel 

On Tue, Feb 3, 2015 at 1:23 PM -0800, "Gregory Farnum" <greg@xxxxxxxxxxx> wrote:

On Tue, Feb 3, 2015 at 1:17 PM, John Spray  wrote:
> On Tue, Feb 3, 2015 at 2:21 PM, Daniel Schneller
>  wrote:
>> Now, say I wanted to put /baremetal into a different pool, how would I go
>> about this?
>>
>> Can I setfattr on the /cephfs mountpoint and assign it a different pool with
>> e. g. different replication settings?
>
> This should make it clearer:
> http://ceph.com/docs/master/cephfs/file-layouts/#inheritance-of-layouts
>
> When you change the layout of a directory, the new layout will only
> apply to newly created files: it will not trigger any data movement.
>
> If you explicitly change the layout of a file containing data to point
> to a different pool, then you will see zeros when you try to read it
> back (although new data will be written to the new pool).

That statement sounds really scary. To reassure people: you can't
actually change layout on a file which has already been written to!
Trying to do so will return an error code; actually changing the
layouts and seeing this result would require manually mucking around
with RADOS data underneath the MDS.
-Greg

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