[gpfsug-discuss] Migration policy confusion

Thu Jul 7 15:30:33 BST 2016

Thanks all.  I realized that my file creation command was building 200k size files instead of the 200MB files.  I fixed that and now I see the mmapplypolicy command take a bit more time and show accurate data as well as my bytes are now on the proper NSDs.  It’s always some little thing that the human messes up isn’t it?  ☺

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 7, 2016 at 9:20 AM
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] Migration policy confusion

At the very least, LOOK at the messages output by the mmapplypolicy command at the beginning and end.
The "occupancy" stats for each pool are shown BEFORE and AFTER  the command does its work.

In even more detail, it shows you how many files and how many KB of data were (or will be or would be) migrated.

Also, options matter.  ReadTheFineManuals.  -I test vs -I defer vs -I yes.

To see exactly which files are being migrated, use -L 2
To see exactly which files are being selected by your rule(s), use -L 3
And for more details about the files being skipped over, etc, etc,   -L 6

Gee, I just checked the doc myself, I forgot some of the details and it's pretty good.
Admittedly mmapplypolicy is a complex command.  You can do somethings simply, only knowing
a few options and policy rules, BUT...

As my father used to say, "When all else fails, read the directions!"

-L n
Controls the level of information displayed by the mmapplypolicy command. Larger values indicate
the display of more detailed information. These terms are used:
candidate file
A file that matches a MIGRATE, DELETE, or LIST policy rule.
chosen file
A candidate file that has been scheduled for action.

These are the valid values for n:
0 Displays only serious errors.
1 Displays some information as the command runs, but not for each file. This is the default.
2 Displays each chosen file and the scheduled migration or deletion action.
3 Displays the same information as 2, plus each candidate file and the applicable rule.
4 Displays the same information as 3, plus each explicitly EXCLUDEed or LISTed file, and the
applicable rule.
5 Displays the same information as 4, plus the attributes of candidate and EXCLUDEed or LISTed
files.
6 Displays the same information as 5, plus non-candidate files and their attributes.

For examples and more information on this flag, see the section: The mmapplypolicy -L command in the
IBM Spectrum Scale: Problem Determination Guide.

--marc

From:        "Mark.Bush at siriuscom.com" <Mark.Bush at siriuscom.com>
To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:        07/07/2016 09:17 AM
Subject:        Re: [gpfsug-discuss] Migration policy confusion
Sent by:        gpfsug-discuss-bounces at spectrumscale.org
________________________________

Thanks Daniel.  I did wait for 15-20 minutes after.

From: <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Daniel Kidger <daniel.kidger at uk.ibm.com>
Reply-To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date: Thursday, July 7, 2016 at 8:10 AM
To: "gpfsug-discuss at spectrumscale.org" <gpfsug-discuss at spectrumscale.org>
Cc: "gpfsug-discuss at spectrumscale.org" <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] Migration policy confusion

Mark,
For performance reasons, mmdf gets its data updated asynchronously.
Did you try waiting a few minutes?
Daniel
Error! Filename not specified.
Error! Filename not specified.

Dr Daniel Kidger
IBM Technical Sales Specialist
Software Defined Solution Sales

+44-07818 522 266
daniel.kidger at uk.ibm.com

----- Original message -----
From: "Mark.Bush at siriuscom.com" <Mark.Bush at siriuscom.com>
Sent by: gpfsug-discuss-bounces at spectrumscale.org
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Cc:
Subject: [gpfsug-discuss] Migration policy confusion
Date: Thu, Jul 7, 2016 2:00 PM

Hello all, I’m struggling trying to understand tiering and policies in general in SpecScale.  I have a single filesystem with two pools defined (system, GOLD).  The GOLD pool is made up of some faster disks than the system pool.  The policy I’m trying to get working is as follows

RULE 'go_gold'

    MIGRATE

        FROM POOL 'system'

    TO POOL 'GOLD'

        WHERE (LOWER(NAME) LIKE '%.perf')

I’m simply trying to get the data to move the NDS’s in GOLD pool.

When I do an mmapplypolicy, mmlsattr shows that it’s now in the GOLD pool but when I do a mmdf the data shows 100% free still.  I tried a mmrestripefs as well and no change to the mmdf output.  Am I missing something here?  Is this just normal behavior and the blocks will get moved at some other time?  I guess I was expecting instant gratification and that those files would have been moved to the correct NSD.

Mark R. Bush| Solutions Architect
Mobile: 210.237.8415 | mark.bush at siriuscom.com
Sirius Computer Solutions | www.siriuscom.com<http://www.siriuscom.com/>
10100 Reunion Place, Suite 500, San Antonio, TX 78216

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