[Lustre-discuss] Query

[Ricardo M. Correia]

Hi Ravi,

On Ter, 2009-01-13 at 11:59 +0530, Ravi Rattihalli wrote:
>  Here are my questions:

>      1. Integrating ZFS with Lustre: Does this mean that some features
>         of ZFS are going to be integrated with Lustre? ( like
>         optimized checksums of ZFS etc ) 

Yes, we plan to integrate some ZFS features with Lustre.

One of such features is the checksumming, like you mentioned. We are
planning to make the Lustre clients compute and provide the checksums
over the wire to the servers, and use them as the block checksums in
ZFS. That will achieve two goals: 1) offload checksum computation to
clients, which in total have more CPU available than servers and 2)
achieve true end-to-end data integrity.

There may also be some integration in terms of quotas, or some other
features.

We will also be developing some features in ZFS, to achieve either
better performance in some cases (e.g., a zero-copy API), or to achieve
new functionality (e.g., multi-mount protection, but this is not our
highest priority right now).
> 
>      1. Which version of Lustre will have end-to-end data interity and
>         which checksum algorithm will be used (if not CRC32)?
> 
> (I read in one document written by Peter Bojanic which said Lustre+ZFS
> = End-to-End Data Integrity) So is it ver. 3.0 and above?

I believe so.
> 
>  I read in wikipedia under ZFS integration “Lustre 3.0 will allow
> users to choose between ZFS and ldiskfs as back-end storage”.
> 
> Why ZFS and ldiskfs are treated separately here even after integration
> here? Once integrated it is just Lustre 3.0 isn’t it?

Yes, but I'm not sure what is your confusion here.

With Lustre 3.0, you will be free to choose whether you wish to create
ldiskfs or ZFS-formatted backend devices - both options should be
available.
> 
>  I would be glad to hear the answers from you which may solve my
> queries and confusionJ

I hope my answers clarify things a bit.

Cheers,
Ricardo