From: Jody McIntyre <[EMAIL PROTECTED]>
Date: Wed, 27 Dec 2006 08:42:42 -0500
Hi John,
On Fri, Dec 22, 2006 at 02:05:35PM -0500, John R. Dunning wrote:
> 1. Does it make sense to structure the OSS<->OST connections as point to
> point links, or am I missing something?
Absolutely. This is, in fact, our recommended configuration. Doing it
this way is less complex and has fewer points of failure compared to a
SAN-like solution. As you've probably figured out, the only thing
Lustre requires is that storage be shared between two OSSes (and MDSes)
for failover purposes. Since most FC controllers are (at least)
dual-ported, this can be done without FC switches.
Right. In fact, the hba we're qualifying is a qlogic 2462 2-port 4Gb unit,
which seems like it should be exactly right for this kind of application.
> 2. Have you run into customer situations where they have an existing SAN
that
> they want to run lustre on?
>
> a. If yes, what issues are involved in configuring it to appear as a
> bunch of disjoint luns and get lustre set up on it?
>
> b. If no, and they instead tend to buy dedicated storage for lustre,
do
> they still want to set it up like a SAN even though it isn't?
Yes, and I'm not aware of any issues. SAN administrators are usually
good at setting things like this up :)
Well, ok, so is it a fair statement to say that the recommended configuration
is to use point-to-point, but if a customer, for whatever reason, wants to use
a SAN-like topology, there's no real downside to that as long as the host-side
software is allowed to treat it as if it was point-to-point? What I'm really
after here is what we should put in our documentation, and what to point users
to when they're trying to work out how to set up their systems.
> 3. Starting from first principles, when talking about a new deployment,
what
> do you recommend, and why?
Keep it as simple as possible - have as few components as you can.
Agreed.
Not using FC switches fits well with this strategy. Also, create LUNs
that are as close to the 8 TB limit as possible so you have fewer OSTs.
In general, Lustre doesn't care about OST count, but this will make
things slightly easier to manage and reduce your chances of running into
full OST problems.
Sure. In our case, it's unlikely that we'll be getting anywhere near 8TB/OST,
because we expect to be far more concerned about bandwidth than capacity. But
I understand the point; aside from anything else, I want to be able to
recommend to people what's the simplest configuration they can use that will
get them the results they're looking for, and part of that means identifying
the smallest set of controllers and things that will do the job.
Thanks...
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