[gpfsug-discuss] inode update delay?

[Keigo Matsubara]

Hi Aaron,

I think the product is designed so that some inode fields are not 
propagated among nodes instantly in order to avoid unnecessary overhead 
within the cluster. See:

Exceptions to Open Group technical standards - IBM Spectrum Scale: 
Administration and Programming Reference - IBM Spectrum Scale 4.2 - IBM 
Knowledge Center
https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.0/com.ibm.spectrum.scale.v4r2.adm.doc/bl1adm_xopen.htm

---
Keigo Matsubara, Industry Architect, IBM Japan
TEL: +81-50-3150-0595, T/L: 6205-0595




From:   Aaron Knister <aaron.s.knister at nasa.gov>
To:     <gpfsug-discuss at spectrumscale.org>
Date:   2016/07/23 13:47
Subject:        [gpfsug-discuss] inode update delay?
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



I've noticed that there can be a several minute delay between the time 
changes to an inode occur and when those changes are reflected in the 
results of an inode scan. I've been working on code that checks ia_xperm 
to determine if a given file has extended acl entries and noticed in 
testing it that the acl flag wasn't getting set immediately after giving 
a file an acl. Here's what I mean:

# cd /gpfsm/dnb32

# date; setfacl -b  acltest*
Sat Jul 23 00:24:57 EDT 2016

# date; /usr/lpp/mmfs/samples/util/tsinode /gpfsm/dnb32 | egrep acl | wc 
-l
Sat Jul 23 00:24:59 EDT 2016
5

# date; /usr/lpp/mmfs/samples/util/tsinode /gpfsm/dnb32 | egrep acl | wc 
-l
Sat Jul 23 00:25:10 EDT 2016
5

# date; /usr/lpp/mmfs/samples/util/tsinode /gpfsm/dnb32 | egrep acl | wc 
-l
Sat Jul 23 00:25:21 EDT 2016
0

I'm a little confused about what's going on here-- is there some kind of 
write-behind for inode updates? Is there a way I can cause the cluster 
to quiesce and flush all pending inode updates (an mmfsctl suspend and 
resume seem to have this effect but I was looking for something a little 
less user-visible)? If I access the directory containing the files from 
another node via the VFS mount then the update appears immediately in 
the inode scan. A mere inode scan from another node w/o touching the 
filesystem mount doesn't necessarily seem to trigger this behavior.

Thanks!

-Aaron

-- 
Aaron Knister
NASA Center for Climate Simulation (Code 606.2)
Goddard Space Flight Center
(301) 286-2776
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