[gpfsug-discuss] LROC Express

[Sanchez, Paul]

I can’t confirm whether it works with Express, since we’re also running standard.  But as a simple test, I can confirm that deleting the gpfs.ext package doesn’t seem to throw any errors w.r.t. LROC in the logs at startup, and “mmdiag --lroc” looks normal when running without gpfs.ext (Standard Edition package).  Since we have other standard edition features enabled, I couldn’t get far enough to actually test whether the LROC was still functional though.

In the earliest 4.1.0.x releases the use of LROC was confused with “serving NSDs” and so the use of the feature required a server license, and it did throw errors at startup about that.  We’ve confirmed that in recent releases that this is no longer a limitation, and that it was indeed erroneous since the goal of LROC was pretty clearly to extend the capabilities of client-side pagepool caching.

LROC also appears to have some rate-limiting (queue depth mgmt?) so you end up in many cases getting partial file-caching after a first read, and a subsequent read can have a mix of blocks served from local cache and from NSD.  Further reads can result in more complete local block caching of the file.  One missing improvement would be to allow its use on a per-filesystem (or per-pool) basis.  For instance, when backing a filesystem with a huge array of Flash or even a GSS/ESS then the performance benefit of LROC may be negligible or even negative, depending on the performance characteristics of the local disk.  But against filesystems on archival media, LROC will almost always be a win.  Since we’ve started to see features using tracked I/O access time to individual NSDs (e.g. readReplicaPolicy=fastest), there’s potential here to do something adaptive based on heuristics as well.  Anyone else using this at scale and seeing a need for additional knobs?

Thx
Paul

From: gpfsug-discuss-bounces at gpfsug.org [mailto:gpfsug-discuss-bounces at gpfsug.org] On Behalf Of Barry Evans
Sent: Monday, June 22, 2015 11:40 AM
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] LROC Express

Hi Bob,

Thanks for this, just to confirm does this mean that it *does not* work with express?

Cheers,
Barry


Bob Oesterlin wrote:
It works with Standard edition, just make sure you have the right license for the nodes using LROC.

Bob Oesterlin
Nuance COmmunications


Bob Oesterlin


On Mon, Jun 22, 2015 at 10:28 AM, Barry Evans <bevans at pixitmedia.com<mailto:bevans at pixitmedia.com>> wrote:
Hi All,

Very quick question for those in the know - does LROC require a standard license, or will it work with Express? I can't find anything in the FAQ regarding this so I presume Express is ok, but wanted to make sure.

Regards,
Barry Evans
Technical Director
Pixit Media/ArcaStream



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