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

[Alex Chekholko]

On 4/11/17 8:36 AM, Marc A Kaplan wrote:
>
> 5) YMMV - We'd love to hear/see your performance results for
> mmapplypolicy, especially if they're good.  Even if they're bad, come
> back here for more tuning tips!

I have a filesystem that currently has 267919775 (roughly quarter 
billion, 250 million) used inodes.  The metadata is on SSD behind a DDN 12K.

We do use 4K inodes, and files smaller than 4K fit into the inodes.

Here is the command I use to apply a policy:

mmapplypolicy gsfs0 -P policy.txt -N 
scg-gs0,scg-gs1,scg-gs2,scg-gs3,scg-gs4,scg-gs5,scg-gs6,scg-gs7 -g 
/srv/gsfs0/admin_stuff/ -I test -B 500 -A 61 -a 4

That takes approximately 10 minutes to do the whole scan.  The "-B 500 
-A 61 -a 4" numbers we determined just by trying different values with 
the same policy file and seeing the resulting scan duration.

10mins is short enough to do almost "interactive" type of file list 
policies and look at the results.  E.g. list all files over 1TB in size.

This was a couple of years ago, probably on a different GPFS version, 
but on same storage and NSD hardware, so now I just copy those 
parameters.  You should probably not just copy them but try some other 
values yourself.

Regards,
Alex