Oak Ridge Leadership Computing Facility

Spider is the name of the OLCF’s center-wide Lustre file system that handles most of the operational work for OLCF systems. It is a large-scale Lustre file system with over 19,500 clients and provides (10) PB of disk space. It has a demonstrated bandwidth of 120 GB/s.

Spider is currently accessible nearly all of the OLCF’s computational resources, including Titan and its 300,000+ compute cores. The file system is available from the following OLCF systems:

• Titan
• Lens
• Smoky
• Frost
• Data Transfer Nodes

Spider provides a location to temporarily store large amounts of data needed and produced by batch jobs. Due to the size of the file system, the area is not backed up. In most cases, a regularly running purge removes data not recently accessed to help ensure available space for all users. Needed data should be copied to more permanent locations.

Spider comprises (3) file systems:

There are a few reasons why having multiple file systems within Spider is advantageous.

More Metadata Servers – Currently each Lustre filesystem can only utilize one Metadata Server (MDS). Interaction with the MDS is expensive; heavy MDS access will impact interactive performance. Providing (3) filesystems allows the load to be spread over (3) MDSs.

Higher Availability – The existence of multiple filesystems increases our ability to keep at least one filesystem available at all times.

Through the PBS gres option, users can specify the scratch area used by their batch jobs so that the job will not start if that file system becomes degraded or unavailable.

Line (5) in the following example will associate a batch job with the widow2 file system. If widow2 becomes unavailable prior to execution of the batch job, the job will be placed on hold until widow2 returns to service.

  1: #!/bin/csh
  2: #PBS -A ABC123
  3: #PBS -l size = 160000
  4: #PBS -l walltime = 08:00:00
  5: #PBS -l gres=widow2
  6:
  7: cd /lustre/widow2/scratch/$USER
  8: aprun -n 120000 a.out

The following example will associate a batch job with the widow2 and widow3 file systems. If either widow2 or widow3 becomes unavailable prior to execution of the batch job, the job will be placed on hold until both widow2 and widow3 are in service.

  -l gres=widow2%widow3

If a batch job is not associated with a file system, i.e., if the gres option is not used, the batch job will be associated with all four widow file systems by adding -l gres=widow1%widow2%widow3 to to the batch submission. A warning message to this effect is printed to stderr.

• Associating a batch job with a file system will prevent the job from running if the file system becomes degraded or unavailable.
• If a batch job only uses (1) or (2) of the spider file systems, specifying the file systems explicitly instead of taking the default of all (4), would prevent the job from being held if a file system not used by the job becomes degraded or unavailable.

The checkjob utility can be used to view a batch job’s file system associations. For example:

  $ qsub -lgres=widow2 batchscript.pbs
  851694.nid00004
  $ checkjob 851694 | grep "Dedicated Resources Per Task:"
  Dedicated Resources Per Task: widow2: 1

A temporary User Work scratch directory is available for each user at (in each Spider file system) at /lustre/widow[1-3]/scratch/$USER

By default, User Work directories are owned by the user, and the group is set to the owning user’s userid-named-group. Permissions are set to 700. Changes to the default permissions by the owning user will be reset hourly for security purposes. Long-term changes to the directory permissions can be requested by contacting OLCF User Assistance Center.

Files in the user scratch directories are subject to the standard purge.

A default file system has been chosen for each user. The /tmp/work/$USER link can be used to access the default directory. A user’s default file system was chosen based on the user’s initial project membership. For example, all users whose initial project membership is climate-centric will be placed on the same file system. All climate-centric Project Work areas are also placed on the same file system. Using the default file system helps spread load over the file systems as well as helps to ease data sharing/access between project members.

A temporary Project Work directory is available for each project on (1) of the (4) Spider file systems. The directory can be accessed through the /tmp/proj/ link.

By default, Project Work directories are owned by the root, the group is set to the project’s group, and permissions are set to 770. Changes to the directory permissions can be requested by contacting OLCF User Assistance Center.

Files in the Project Work directories are not currently subject to the standard purge. However, this is subject to change and users should always consider Spider temporary storage.

Use ls – The following ls command can be used to determine where a link points. The target location’s path will specify the file system on which the directory exists:

  ls -ld /tmp/work/$USER
  ls -ld /tmp/proj/

Use spiderinfo – The spiderinfo utility will list each file system’s status as well as the calling user’s /tmp/work and /tmp/proj file systems:

  $ spiderinfo

    Current lustre status (Tue Jan 25 14:32:27 2011):
    widow1 (up), widow2 (up), widow3 (up)

    Lustre directory information for user 'joe'
    /tmp/work/joe: widow2 (up)
    /tmp/proj/abc123: widow2 (up)

More information on Spider and Lustre can be found on the Spider Best Practices page and the Lustre Basics page.