[gpfsug-discuss] RAID type for system pool

[Marc A Kaplan]

1. (Guessing) perhaps it was considered useful to distinguish inode 
traffic from log traffic and just lump other metadata together.
2. A 512 byte inode has space for up to 384 bytes of data-in-inode data. 
(Says tsdbfs )




From:   "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   09/11/2018 11:49 AM
Subject:        Re: [gpfsug-discuss] RAID type for system pool
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



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> 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>
To:        gpfsug main discussion list <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




From: 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

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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