[Lustre-devel] Lustre HSM HLD draft

[Peter Braam <Peter.Braam@Sun.COM>]

Versions are critical - we need them for multiple things, let's make 
sure we get exactly the right thing in ZFS also.

- Peter -

Andreas Dilger wrote:
> On Feb 08, 2008  16:55 +0100, Aurelien Degremont wrote:
>   
>> But the touch could be problematic. Lustre gurus, is there another time 
>> field we could use instead ? Should we add a 
>> "last-modification-field-which-ignore-touch" ? Is this really a problem 
>> is we use display a "touched" time ? In this case, we display what the 
>> user set on the file, we suppose he did it in purpose.
>>     
>
> There was work done in ext4/ldiskfs to add a 64-bit "version" field to
> the on-disk inode, for use by lustre and NFSv4.  In the ldiskfs case
> Lustre was free to store any information in this field it wanted.  The
> planned use for this field is for "version based recovery" and it has
> the semantic that it is an increasing (though not necessarily sequential)
> version number that tracks any change to the file.  This is stored in
> each inode on the MDT and each object on the OSTs.
>
> In ZFS I believe there is also a "last modified transaction group" (txg)
> number stored with each dnode that could be used in a similar manner.
>
> Cheers, Andreas
> --
> Andreas Dilger
> Sr. Staff Engineer, Lustre Group
> Sun Microsystems of Canada, Inc.
>
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>   
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