[gpfsug-discuss] Policy scan against billion files for ILM/HSM

[Frederick Stock]

As Zachary noted the location of your metadata is the key and for the 
scanning you have planned flash is necessary.  If you have the resources 
you may consider setting up your flash in a mirrored RAID configuration 
(RAID1/RAID10) and have GPFS only keep one copy of metadata since the 
underlying storage is replicating it via the RAID.  This should improve 
metadata write performance but likely has little impact on your scanning, 
assuming you are just reading through the metadata.

Fred
__________________________________________________
Fred Stock | IBM Pittsburgh Lab | 720-430-8821
stockf at us.ibm.com



From:   Zachary Giles <zgiles at gmail.com>
To:     gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:   04/11/2017 12:49 AM
Subject:        Re: [gpfsug-discuss] Policy scan against billion files for 
ILM/HSM
Sent by:        gpfsug-discuss-bounces at spectrumscale.org



It's definitely doable, and these days not too hard. Flash for
metadata is the key.
The basics of it are:
* Latest GPFS for performance benefits.
* A few 10's of TBs of flash ( or more ! ) setup in a good design..
lots of SAS, well balanced RAID that can consume the flash fully,
tuned for IOPs, and available in parallel from multiple servers.
* Tune up mmapplypolicy with -g somewhere-on-gpfs; --choice-algorithm
fast; -a, -m and -n to reasonable values ( number of cores on the
servers ); -A to ~1000
* Test first on a smaller fileset to confirm you like it. -I test
should work well and be around the same speed minus the migration
phase.
* Then throw ~8 well tuned Infiniband attached nodes at it using -N,
If they're the same as the NSD servers serving the flash, even better.

Should be able to do 1B in 5-30m depending on the idiosyncrasies of
above choices. Even 60m isn't bad and quite respectable if less gear
is used or if they system is busy while the policy is running.
Parallel metadata, it's a beautiful thing.



On Tue, Apr 11, 2017 at 12:29 AM, Masanori Mitsugi
<mitsugi at linux.vnet.ibm.com> wrote:
> Hello,
>
> Does anyone have experience to do mmapplypolicy against billion files 
for
> ILM/HSM?
>
> Currently I'm planning/designing
>
> * 1 Scale filesystem (5-10 PB)
> * 10-20 filesets which includes 1 billion files each
>
> And our biggest concern is "How log does it take for mmapplypolicy 
policy
> scan against billion files?"
>
> I know it depends on how to write the policy,
> but I don't have no billion files policy scan experience,
> so I'd like to know the order of time (min/hour/day...).
>
> It would be helpful if anyone has experience of such large number of 
files
> scan and let me know any considerations or points for policy design.
>
> --
> Masanori Mitsugi
> mitsugi at linux.vnet.ibm.com
>
> _______________________________________________
> gpfsug-discuss mailing list
> gpfsug-discuss at spectrumscale.org
> http://gpfsug.org/mailman/listinfo/gpfsug-discuss



-- 
Zach Giles
zgiles at gmail.com
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