[Lustre-devel] Lustre HSM - some talking points.

Vicky White vyw at ornl.gov
Mon Feb 2 11:54:06 PST 2009

Colin Ngam wrote:
> I do not see why we need to query these EAs in normal operation.  
> These EAs will only be accessed when we need to perform Ultimate 
> Disaster Recovery - when you have lost all data on disks and all you 
> have are tapes.

That would help.  I don't know what it would cost to store the EA in a 
separate object to begin with, though, and that would be incurred on 
every file.   Plus you have to consider the space it takes up.

> I was thinking about XML - but it is "opaque" to Object SAMQFS so, it 
> is up to the Lustre side.  Whatever it is, the Applications - 
> Lustre-Restore for example, is the one that has to understand the 
> format.  I am not a Tar Header expert - but I assume that these EAs 
> can go with the file in the tar ball.

I think what you put in the tar ball is up to you.   Putting the EAs in 
there regardless of what the hsm was might simplify the design, so you 
wouldn't have to extract the EA in a different way for each hsm.

I was just trying to keep the hpss EA design in front of folks so that 
if we were considering using that, we knew all the tradeoffs.

> I do not expect to keep any of it on line on disk cache, on the SAMFS 
> side.  I see no reason.
> With respect to whether it should be consistent with HPSS - I would 
> say if that is all we need and it is sufficient - why not.  Otherwise, 
> let's make it better than HPSS.  It must be in SUN's best interest to 
> sell SAMQFS?

Oh, I'm sure it is.

> I do apologize Vicky, are you a SUN employee?

No.   Were you going to feel sorry for me if I worked for Sun? ;)


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