[gpfsug-discuss] RAID type for system pool

[Buterbaugh, Kevin L]

Hi Marc,

Understood … I’m just trying to understand why some I/O’s are flagged as metadata, while others are flagged as inode?!?  Since this filesystem uses 512 byte inodes, there is no data content from any files involved (for a metadata only disk), correct?  Thanks…

Kevin

On Sep 11, 2018, at 9:12 AM, Marc A Kaplan <makaplan at us.ibm.com<mailto:makaplan at us.ibm.com>> wrote:

Metadata is anything besides the data contents of your files.
Inodes, directories, indirect blocks, allocation maps, log data ...  are the biggies.

Apparently, --iohist may sometimes distinguish some metadata as "inode", "logData", ...  that doesn't mean those aren't metadata also.




From:        "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu<mailto:Kevin.Buterbaugh at Vanderbilt.Edu>>
To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Date:        09/10/2018 03:12 PM
Subject:        [gpfsug-discuss]  RAID type for system pool
Sent by:        gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>
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From: gpfsug-discuss-owner at spectrumscale.org<mailto:gpfsug-discuss-owner at spectrumscale.org>
Subject: Re: [gpfsug-discuss] RAID type for system pool
Date: September 10, 2018 at 11:35:05 AM CDT
To: klb at accre.vanderbilt.edu<mailto:klb at accre.vanderbilt.edu>

Hi All,

So while I’m waiting for the purchase of new hardware to go thru, I’m trying to gather more data about the current workload.  One of the things I’m trying to do is get a handle on the ratio of reads versus writes for my metadata.

I’m using “mmdiag —iohist” … in this case “dm-12” is one of my metadataOnly disks and I’m running this on the primary NSD server for that NSD.  I’m seeing output like:

11:22:13.931117  W       inode    4:299844163        1    0.448  srv   dm-12                 <redacted>
11:22:13.932344  R    metadata    4:36659676         4    0.307  srv   dm-12                 <redacted>
11:22:13.932005  W     logData    4:49676176         1    0.726  srv   dm-12                 <redacted>

And I’m confused as to the difference between “inode” and “metadata” (I at least _think_ I understand “logData”)?!?  The man page for mmdiag doesn’t help and I’ve not found anything useful yet in my Googling.

This is on a filesystem that currently uses 512 byte inodes, if that matters.  Thanks…

Kevin
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