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Subject: Re: [MTT users] Patch to add --local-scratch option
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-09-18 09:00:18

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.

> 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).

> 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.

I'm looking at the patch in detail now... sorry for the delay...

Jeff Squyres
Cisco Systems