[Twg] Lustre Requirements and Roadmap

[Christopher J. Morrone]

John,

Thanks for creating that list!

I think that for the metadata performance, we should use labels other 
than "min" and "max".  After all, we would never say "no, we won't 
accept a filesystem that is capable of more than than this". :)

Also, the requirements are only useful if we can give target dates for 
the requirements.  So maybe the "min" column becomes Q3/2012, and the 
max column Q1/2014.  I am just pulling those dates out of thin air, they 
could be something else.

I think we should split the aggregate and single client file creates/sec 
requirements into two separate requirement lines.

For backend storage:

I think that we should take out the "framework to enable alternatives to 
ldiskfs" line.  That is a design decision rather than a requirement.  I 
think it is certainly necessary given the requirements, but if we are 
trying to distinguish between requirements and architectural decisions, 
that line should be removed.

Rather than "no performance impact", say "low performance impact".  Zero 
impact is probably impossible. :)   At some point we need to be clear on 
exactly what quilifies as "low".  One part of that might be:

   - The solution must perform filesystem integrity checking and repair
     on-line.

I.E., There may be no required downtime just for consistence checking 
and repair.

What is the rationale for the "direct I/O mode" requirement?  Not that I 
am opposed to it...but is that really a requirement, or a solution?

For end-to-end integrity, I would suggest that T10 PI is not sufficient, 
since it only concerns itself with the path between the HBA and the 
backend storage (disks/flash).  I think that we need to define where the 
"ends" are, and they should really extend up into memory on the lustre 
servers.  T10 DIF + Oracle's DIX might be a better example.  Examples 
are not necessarily what we want here.

Chris

On 01/27/2011 09:24 AM, John Carrier wrote:

> The following is an incomplete list of requirements to motivate further
> discussion :
>
>     * metadata performance
>
>        GOAL: improve file system scalability and interactive
>              performance
>
>        requirements:                    min            max
>        -  # files in file system    100 billion       1 trillion
>        -  # files in directory       50 million      10 billion
>        -  file creates / sec        100 thousand     30 thousand
>                                       (aggregate)      (single client)
>        -  directory lisings / sec
>        -  open files per process        -           100 thousand
>        -  file system capacity       30 PB          100 PB
>        -  # clients                  30 thousand    ?00 thousand
>
>
>     * backend storage
>
>        GOAL: provide reliable, scalable backing store for
>              Lustre servers
>
>        requirements:
>        -  large LUNs (min 32 TB)
>        -  end-to-end data integrity (T10 PI or equivalent)
>        -  no performance impact for file system repair
>        -  framework to enable alternatives to ldiskfs
>        -  direct I/O mode
>        -  ??
>
>
>
>
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