[gpfsug-discuss] wanted...gpfs policy that places larger files onto a pool based on size

Jez Tucker jez.tucker at gpfsug.org
Mon Oct 31 17:20:30 GMT 2016


Hey Bryan

   There was a previous RFE for path placement from the UG, but Yuri 
told me this was not techically possible as an inode has no knowledge 
about the parent dentry.  (IIRC).    You can see this in effect in the C 
API.  It is possible to work this out at kernel level, but it's so 
costly that it becomes non-viable at scale / performance.

IBMers please chip in and expand if you will.

Jez

On 31/10/16 17:09, Bryan Banister wrote:
>
> The File Placement Policy that you are trying to set cannot use the 
> size of the file to determine the placement of the file in a GPFS 
> Storage Pool.  This is because GPFS has no idea what the file size 
> will be when the file is open()’d for writing.
>
> Hope that helps!
>
> -Bryan
>
> PS. I really wish that we could use a path for specifying data 
> placement in a GPFS Pool, and not just the file name, owner, etc.  
> I’ll submit a RFE for this.
>
> *From:*gpfsug-discuss-bounces at spectrumscale.org 
> [mailto:gpfsug-discuss-bounces at spectrumscale.org] *On Behalf Of *J. 
> Eric Wonderley
> *Sent:* Monday, October 31, 2016 11:53 AM
> *To:* gpfsug main discussion list
> *Subject:* [gpfsug-discuss] wanted...gpfs policy that places larger 
> files onto a pool based on size
>
> I wanted to do something like this...
>
>
> [root at cl001 ~]# cat /opt/gpfs/home.ply
> /*Failsafe migration of old small files back to spinning media 
> pool(fc_8T) */
> RULE 'theshold' MIGRATE FROM POOL 'system' THRESHOLD(90,70) 
> WEIGHT(ACCESS_TIME) TO POOL 'fc_8T'
> /*Write files larger than 16MB to pool called "fc_8T" */
> RULE 'bigfiles' SET POOL 'fc_8T' WHERE FILE_SIZE>16777216
> /*Move anything else to system pool */
> RULE 'default' SET POOL 'system'
>
> Apparently there is no happiness using FILE_SIZE in a placement policy:
> [root at cl001 ~]# mmchpolicy home /opt/gpfs/home.ply
> Error while validating policy `home.ply': rc=22:
> PCSQLERR: 'FILE_SIZE' is an unsupported or unknown attribute or 
> variable name in this context.
> PCSQLCTX: at line 4 of 6: RULE 'bigfiles' SET POOL 'fc_8T' WHERE 
> {{{FILE_SIZE}}}>16777216
> runRemoteCommand_v2: cl002.cl.arc.internal: tschpolicy /dev/home 
> /var/mmfs/tmp/tspolicyFile.mmchpolicy.113372 -t home.ply   failed.
> mmchpolicy: Command failed. Examine previous error messages to 
> determine cause.
>
> Can anyone suggest a way to accomplish this using policy?
>
>
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