File System

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Revision as of 16:35, 22 January 2014 by Toddr (talk | contribs) (Scratch (short-term storage))

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CCI is moving to the unified GPFS file system.

General Layout

The Unified CCI GPFS filesystem is built using a block size of 8MiB. Performance testing indicated this was about optimal for our storage system hardware. Applications using large-record I/O will benefit most from the large block size. Performance testing shows that applications with small-record I/O perform at least nearly as well with the large block size as in a file system with a much smaller block size.

The file system is broken into three main areas: home, scratch, and barn. Each area of the filesystem has its own purpose and merits.




Home contains user home directories, organized by projects. User home directories are only writable by the user. This area of the filesystem has a 10 GiB quota and is the only area of the filesystem that uses replication to protect data.

Please note: In GPFS, files are counted twice during quota calculations when they are replicated. This means the home directory limit is effectively 5 GiB per project (shared + every user's home).

Home directories are intended to store only your "dot files" and maybe a few other configuration files, scripts, or small programs you need to customize your working environment. Program files, data sets, etc. should be stored in your barn.

Scratch (short-term storage)

There is a scratch data directory for each project and the associated users. as well as corresponding links in each user's home directory. This space is meant as a temporary staging area for performing computation. Performance in this directory will be better than in the home directory. This space does not have a quota.

Each home directory contains a link, scratch, to the user's personal scratch space, and a link, scratch-shared, to the project's shared scratch space.

Important: This space will periodically be purged of files older than 14 days. This policy is subject to change based on filesystem demands. If longer-term storage of data is necessary it should be stored in the barn area.

Barn (long-term storage)

There is a barn directory for each project and the associated users with corresponding links in each user's home directory. This space is meant to allow for longer-term storage of working data and programs than allowed by the scratch area. It is not meant for long-term retention of results. This space has a 10G quota and is not replicated, nor is it purged of old files. Project users must manage their own space usage in the barn.

Additional space may be allocated to a project's barn at the discretion of the CCI Director upon written request by the project PI. Any extended quotas are subject to periodic review and potential reduction at the discretion of the Director.