[gpfsug-discuss] SOBAR questions

[Marc A Kaplan]

I worked on some aspects of SOBAR, but without studying and testing the 
commands - I'm not in a position right now to give simple definitive 
answers - 
having said that....

Generally your questions are reasonable and the answer is: "Yes it should 
be possible to do that, but you might be going a bit beyond the design 
point..,
so you'll need to try it out on a (smaller) test system with some smaller 
tedst files.

Point by point.

1. If SOBAR is unable to restore a particular file, perhaps because the 
premigration did not complete -- you should only lose that particular 
file,
and otherwise "keep going". 

2. I think SOBAR helps you build a similar file system to the original, 
including block sizes.  So you'd have to go in and tweak the file system 
creation step(s).
I think this is reasonable... If you hit a problem... IMO that would be a 
fair APAR.

3. Similar to 2.





From:   "Simon Thompson (Research Computing - IT Services)" 
<S.J.Thompson at bham.ac.uk>
To:     "gpfsug-discuss at spectrumscale.org" 
<gpfsug-discuss at spectrumscale.org>
Date:   01/20/2017 10:44 AM
Subject:        [gpfsug-discuss] SOBAR questions
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



We've recently been looking at deploying SOBAR to support DR of some of
our file-systems, I have some questions (as ever!) that I can't see are
clearly documented, so was wondering if anyone has any insight on this.

1. If we elect not to premigrate certain files, are we still able to use
SOBAR? We are happy to take a hit that those files will never be available
again, but some are multi TB files which change daily and we can't stream
to tape effectively.

2. When doing a restore, does the block size of the new SOBAR'd to
file-system have to match? For example the old FS was 1MB blocks, the new
FS we create with 2MB blocks. Will this work (this strikes me as one way
we might be able to migrate an FS to a new block size?)?

3. If the file-system was originally created with an older GPFS code but
has since been upgraded, does restore work, and does it matter what client
code? E.g. We have a file-system that was originally 3.5.x, its been
upgraded over time to 4.2.2.0. Will this work if the client code was say
4.2.2.5 (with an appropriate FS version). E.g. Mmlsfs lists, "13.01
(3.5.0.0) Original file system version" and "16.00 (4.2.2.0) Current file
system version". Say there was 4.2.2.5 which created version 16.01
file-system as the new FS, what would happen?

This sort of detail is missing from:
https://www.ibm.com/support/knowledgecenter/STXKQY_4.2.2/com.ibm.spectrum.s

cale.v4r22.doc/bl1adv_sobarrestore.htm

But is probably quite important for us to know!

Thanks

Simon

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