[gpfsug-discuss] [EXTERNAL] How to shrink GPFS on DSSG's?

[Peter Childs]

Having only just got an ESS I'm still learning how GNR works. as I read it there are currently two "breeds" of GNR, the version on the "DSS and ESS appliances" and the one in "Erasure Code Edition"

As I understand it from past talks using mmdeldisk to remove a disk works fine in none GNR editions but is not the best way to do the task.

My understanding is that you should

mmchdisk suspend/empty # so new data is not put on the disk but the disk remains available for read.
mmrestripefs -m # to move the data off the disk
mmdeldisk # to actually remove the disk which should be fast as its already been emptied.

We have done this with success in the past to migrate data between Raid6 arrays, with success.

I believe there are some commands with mmvdisk to re-shape recovery groups in GNR but I've not as yet worked out how they work.




Peter Childs

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From: gpfsug-discuss <gpfsug-discuss-bounces at gpfsug.org> on behalf of Jaime Pinto <pinto at scinet.utoronto.ca>
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Subject: [EXTERNAL] [gpfsug-discuss] How to shrink GPFS on DSSG's?

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I'm wondering if it's possible to shrink GPFS gracefully. I've seen some references to that effect on some presentations, however I can't find detailed instructions on any formal IBM documentation on how to do it.

About 3 years ago we launched a new GPFS deployment with 3 DSS-G enclosures (9.6PB usable).
Some 1.5 years later we added 2 more enclosures, for a total of 16PB, and only 7PB occupancy so far.

Basically I'd like to return to the original 3 enclosures, and still maintain the (8+2p) parity level.

Any suggestions?
Thanks
Jaime

---
Jaime Pinto - Storage Analyst
SciNet HPC Consortium - www.scinet.utoronto.ca
University of Toronto

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