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Subject: Re: [MTT users] Patch to add --local-scratch option
From: Tim Mattox (timattox_at_[hidden])
Date: 2008-09-18 10:11:19


I Guess I should comment on Jeff's comments too.

On Thu, Sep 18, 2008 at 9:00 AM, Jeff Squyres <jsquyres_at_[hidden]> wrote:
> On Sep 16, 2008, at 12:07 PM, Ethan Mallove wrote:
>
>> What happens if one uses --local-scratch, but leaves out the
>> --scratch option? In this case, I think MTT should assume
>> --scratch is the same as --local-scratch.
>
> In this case, my $0.02 is that it should be an error. --scratch implies a
> --local-scatch, but I don't think the implication should go the other way.

Yeah, I agree, especially if we call it --mpi-install-scratch.

>> Could the "local" in --local-scratch ever be misleading?
>> Couldn't a user ever use a mounted filesystem that's faster
>> than all their local filesystem? Should it be
>> --fast-scratch?
>
> Mmm... good point. What if we name it what it really is:
> --mpi-install-scratch? This also opens the door for other phase scratches
> if we ever want them. And it keeps everything consistent and simple (from
> the user's point of view).

Ah, yeah, ok, now I see why you wouldl call it --mpi-install-scratch, so
that it matches the MTT ini section name. Sure, that works for me.

>> For future work, how about --scratch taking a (CSV?) list of
>> scratch directories. MTT then does a quick check for which
>> is the fastest filesystem (if such a check is
>> possible/feasible), and proceeds accordingly. That is, doing
>> everything it possible can in a fast scratch (builds,
>> writing out metadata, etc.), and installing the MPI(s) into
>> the slow mounted scratch. Would this be possible?
>
> Hmm. I'm not quite sure how that would work -- "fastest" is a hard thing to
> determine. What is "fastest" at this moment may be "slowest" 2 minutes from
> now, for example.

Yeah, I claim that auto-detecting file system speed is outside the
scope of MTT. :-)

> I'm looking at the patch in detail now... sorry for the delay...
>
> --
> Jeff Squyres
> Cisco Systems
>
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-- 
Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/
 tmattox_at_[hidden] || timattox_at_[hidden]
 I'm a bright... http://www.the-brights.net/