[gpfsug-discuss] Follow-up: migrating billions of files

[Venkateswara R Puvvada]

AFM based migration provides near-zero downtime and supports migrating 
EAs/ACLs including immutability attributes (if home is Scale/ESS). I would 
recommend starting migration in read-only mode, prefetch most of the data 
and convert the fileset to local-updates (if backup is not needed during 
the migration) or independent-writer mode before moving the applications 
to the AFM cache filesets. AFM now supports (from 5.0.2) directory level 
prefetch with many performance improvements and does not require 
list-files to be specified.

~Venkat (vpuvvada at in.ibm.com)



From:   "Oesterlin, Robert" <Robert.Oesterlin at nuance.com>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   03/06/2019 06:14 PM
Subject:        [gpfsug-discuss] Follow-up: migrating billions of files
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



Some of you had questions to my original post. More information:
 
Source:
- Files are straight GPFS/Posix - no extended NFSV4 ACLs
- A solution that requires $’s to be spent on software (ie, Aspera) isn’t 
a very viable option
- Both source and target clusters are in the same DC
- Source is stand-alone NSD servers (bonded 10g-E) and 8gb FC SAN storage
- Approx 40 file systems, a few large ones with 300M-400M files each, 
others smaller
- no independent file sets
- migration must pose minimal disruption to existing users
 
Target architecture is a small number of file systems (2-3) on ESS with 
independent filesets
- Target (ESS) will have multiple 40gb-E links on each NSD server (GS4)
 
My current thinking is AFM with a pre-populate of the file space and 
switch the clients over to have them pull data they need (most of the data 
is older and less active) and them let AFM populate the rest in the 
background.
 
 
Bob Oesterlin
Sr Principal Storage Engineer, Nuance
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