[Beowulf] Clearing out scratch space

[Dmitri Chubarov]

Hello, John,

In HLRS they have what they call a Workspace mechanism (
https://wickie.hlrs.de/platforms/index.php/Workspace_mechanism) where each
user
creates a scratch directory for their project under $SCRATCH_ROOT that has
end-of-life time encoded in the name and a symlink to this directory
in their persistent storage directory tree. A cronjob enforces the end of
life policy.

One advantage is that it is very easy for the admin to extend the lifespan
when it is absolutely needed. It requires only renaming one directory to
extend, for example, the lifetime
of millions of files from genomic applications.

Here at Novosibirsk University where users are getting their resources for
free this mechanism has been reimplemented to ensure that shared storage
does not turn into a file archive.
The main shared storage is an expensive PanFS system that is split into two
partitions: a larger scratch partitions with a directory lifetime limit of
90 days and a smaller $HOME partition.

Some users in fact are abusing the system by recreating a new scratch
directory every 90 days and copying the data along effectively creating
persistent storage. However most of the users do evacuate their valuable
data on time.

Greetings from sunny Siberia,
  Dima
sys and it works by setting draconian limits

On Tue, 12 Jun 2018 at 15:06, John Hearns via Beowulf <beowulf at beowulf.org>
wrote:

> In the topic on avoiding fragmentation Chris Samuel wrote:
>
> >Our trick in Slurm is to use the slurmdprolog script to set an XFS project
> >quota for that job ID on the per-job directory (created by a plugin which
> >also makes subdirectories there that it maps to /tmp and /var/tmp for the
> >job) on the XFS partition used for local scratch on the node.
>
> I had never thought of that, and it is a very neat thing to do.
> What I would like to discuss is the more general topic of clearing files
> from 'fast' storage.
> Many sites I have seen have dedicated fast/parallel storage which is
> referred to as scratch space.
> The intention is to use this scratch space for the duration of a project,
> as it is expensive.
> However I have often seen that the scratch space i used as permanent
> storage, contrary to the intentions of whoever sized it, paid for it and
> installed it.
>
> I feel that the simplistic 'run a cron job and delete files older than N
> days' is outdated.
>
> My personal take is that heirarchical storage is the answere,
> automatically pushing files to slower and cheaper tiers.
>
> But the thought struck me - in the Slurm prolog script create a file called
> THESE-FILES-WILL-SELF-DESTRUCT-IN-14-DAYS
> Then run a cron job to decrement the figure 14
> I guess that doesnt cope with running multiple jobs on the same data set -
> but then again running a job marks that data as 'hot' an dyou reset the
> timer to 14 days.
>
> What do most sites do for scratch space?
>
>
>
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