[gpfsug-discuss] Underlying LUN mirroring NSD impact

[Marc A Kaplan]

Does the mirrored-storage vendor guarantee the sequence of all writes to 
all the LUNs at the remote-site exactly matches the sequence of writes to 
the local site....? If not..   the file system on the remote-site could be 
left in an inconsistent state when the communications line is cut... 

Guaranteeing sequencing to each LUN is not sufficient, because  a typical 
GPFS file system has its data and metadata spread over several LUNs.



From:   "Olaf Weiser" <olaf.weiser at de.ibm.com>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   03/14/2018 07:19 PM
Subject:        Re: [gpfsug-discuss] Underlying LUN mirroring NSD impact
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



HI Mark.. yes.. that's  possible...  at least ,  I'm sure.. there was a 
chapter in the former advanced admin guide of older releases with PPRC .. 
how to do that.. 
similar to PPRC , you might use other methods , but from gpfs perspective 
this should'nt make a difference.. 

and I had have a german customer, who was doing this for years... (but it 
is some years back meanwhile ... hihi time flies...) 





From:        Mark Bush <Mark.Bush at siriuscom.com>
To:        "gpfsug-discuss at spectrumscale.org" 
<gpfsug-discuss at spectrumscale.org>
Date:        03/14/2018 09:11 PM
Subject:        [gpfsug-discuss] Underlying LUN mirroring NSD impact
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



Is it possible (albeit not advisable) to mirror LUNs that are NSD’s to 
another storage array in another site basically for DR purposes?  Once 
it’s mirrored to a new cluster elsewhere what would be the step to get the 
filesystem back up and running.  I know that AFM-DR is meant for this but 
in this case my client only has Standard edition and has mirroring 
software purchased with the underlying disk array.
 
Is this even doable? 
 
 
Mark
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