[gpfsug-discuss] NDS in Two Site scenario

[Mark.Bush at siriuscom.com]

Well said Marc.  I think in IBM’s marketing pitches they make it sound so simple and easy.  But this doesn’t take the place of well planned, tested, and properly sized implementations.

From: <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Marc A Kaplan <makaplan at us.ibm.com>
Reply-To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date: Thursday, July 21, 2016 at 8:33 AM
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] NDS in Two Site scenario

I don't know.  That said, let's be logical and cautious.

Your network performance has got to be comparable to (preferably better than!)  your disk/storage system.
Think speed, latency, bandwidth, jitter, reliability, security.
For a production system with data you care about, that probably means a dedicated/private/reserved channel, probably on private or leased fiber.

Sure you can cobble together a demo, proof-of-concept, or prototype with less than that, but are you going to bet your career, life, friendships, data on that?

Then you have to work through and test failure and recover scenarios...

This forum would be one place to gather at least some anecdotes from power users/admins who might be running GPFS clusters spread over
multiple kilometers...

Is there a sale or marketing team selling this?  What do they recommend?

Here is an excerpt from an IBM white paper I found by googling...  Notice the qualifier "high quality wide area network":

"...Synchronous replication works well for many workloads by replicating data across storage arrays within a data center, within a campus or across geographical distances using high quality wide area network connections. When wide area network connections are not high performance or are not reliable, an asynchronous approach to data replication is required. GPFS 3.5 introduces a feature called Active File Management (AFM). ..."

Of course GPFS has improved (and been renamed!) since 3.5 but 4.2 cannot magically compensate for a not-so-high-quality network!




From:        "Mark.Bush at siriuscom.com" <Mark.Bush at siriuscom.com>
To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:        07/20/2016 07:34 PM
Subject:        Re: [gpfsug-discuss] NDS in Two Site scenario
Sent by:        gpfsug-discuss-bounces at spectrumscale.org
________________________________



Marc, what you are saying is anything outside a particular data center shouldn’t be part of a cluster?  I’m not sure marketing is in line with this then.

From: <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Marc A Kaplan <makaplan at us.ibm.com>
Reply-To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date: Wednesday, July 20, 2016 at 4:52 PM
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] NDS in Two Site scenario

Careful! You need to plan and test, test and plan both failure scenarios and performance under high network loads.
I don't believe GPFS was designed with the idea of splitting clusters over multiple sites.
If your inter-site network runs fast enough, and you can administer it well enough -- perhaps it will work well enough...

Hint: Think about the what the words "cluster" and "site" mean.

GPFS does have the AFM feature, which was designed for multi-site deployments.

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