User Tools

Site Tools


guide:lustre

The Lustre Parallel File System

Lustre on Lengau

Lengau has 16 OSSs arranged in pairs. There are 96 OSTs connected to the 8 pairs. Each OST has an approx. capacity of 43GiB giving a total Lustre storage of 4PiB. Each OSS pair connects to 12 OSTs. Should one OSS in a pair succumb, the other still retains access to all 12 OSTs.

Lustre tools

The main tool for displaying information on the files and directories of a Lustre file system is lfs.

Searching

Use lfs find (instead of the standard GNU find command) to search for Lustre files based on their metadata properties (size, striping, OSTs, etc.).

To find all files larger than 1GB:

lfs find <dirname> -size +1G

To find all files newer than 60 days:

lfs find <dirname> -ctime -60

Best practices

Lustre is designed for parallel access to large files. It accomplishes this by using striping to distribute the contents of a large file across several disk arrays (OSTs) to enable fast parallel IO.

Striping

The standard recommendation from the Lustre developers is:

  • Files smaller than 1GB should be left with the default striping (1)
  • Between 1GB and 10GB a small stripe should be used (2)
  • 10 to 100GB : use medium striping (2 to 4)
  • Above 100GB: use maximum striping (-c -1)
    Use only this last option with individual files that you know will be above 100GB or use highly parallelized access.

To set the striping for a file to 2

lfs setstripe -c 2 <filename>

To change the default striping applied to files in a sub-directory to 2 (and only applied to files larger than 1G)

lfs setstripe -c 2  -s 1G <dirname>
Check this ^^^.

Note:

  • When you change the settings for an existing file, the file will actually only change to the new striping when it is recreated.
  • The same applies when you change the settings for an existing directory. You will need to rename the directory, create a new directory with the new stripe settings, and then copy (not move) the files to the new directory to inherit the new settings.

See lfs migrate for more.

/var/www/wiki/data/pages/guide/lustre.txt · Last modified: 2020/05/06 11:55 by kevin