Filesystems:Frontenac
Overview
The Frontenac cluster uses a shared GPFS filesystem for all file storage.
User files are located under /global/home of 3TB quota, shared project space under /global/project, and network scratch space under /global/scratch of 5TB quota.
In addition to the network storage, each compute node has a 1.5TB local hard disk for fast access to local scratch space by jobs using the location specified by the $TMPDISK environment variable. All files in the local scratch space are assumed to be deleted automatically when corresponding jobs finish.
Note that it is the user's responsibility to manage the age of their data: these filesystems do not provide archiving. If data are no longer needed, they need to be moved off the system. If you need assistance with this, please contact us.
Storage Areas
Unlike your personal computer, a Compute Canada system will typically have several storage spaces or filesystems and you should ensure that you are using the right space for the right task. In this section we will discuss the principal filesystems available on most Compute Canada systems and the intended use of each one along with its characteristics. Storage options are distinguished by the available hardware, access mode and write system. Typically, most Compute Canada systems offer the following storage types:
- Global Parallel File System (GPFS)
- This file system is visible on both login and compute nodes. Combining multiple disk arrays and fast servers, it offers excellent performance for large files and large input/output operations. Two types of storage are distinguished on such systems: long term storage and temporary storage (scratch). Performance is subject to variations caused by other users.
- Local Filesystem
- This is a local hard drive attached to each of the nodes. Its advantage is high performance (because it is rarely shared). Its disadvantage is that local files must be re-copied to a global area to be vi sible on other nodes such as the login ()workup) node. Typically, local disk is regularly "cleaned", i.e. data kept there are considered transitory.
- RAM (memory) Filesystem
- This is a filesystem that exists within a node's RAM, so it reduces the available memory. This makes it very fast but low-capacity. A RAM disk must be cleaned at the end of a job.
The following table summarizes the properties of these storage types.
| Type | Accessibility | Throughput | Latency | Longevity |
|---|---|---|---|---|
| GPFS (/global/home, /global/project ...) | All nodes | Fair | High | Long term |
| GPFS (/global/scratch) | All nodes | Fair | High | Short term (periodically cleaned) |
| Local Filesystem (TMPDIR) | Local to the node | Fair | Medium | Very short term |
| Memory (RAM) FS | Local to the node | Good | Very low | Very short term, cleaned after every job |
Throughput describes the efficiency of the file system for large operations. Sometimes also called "bandwidth" in the context of FS-IO.
Latency describes the efficiency of the file system for small operations. Low latency is good.
Best practices
- Avoid text format files for large data.
- Use local storage for temporary files. The scheduler provides this (
$SLURM_TMPDIR). - Searches should be done in memory rather than on disk.
- Regularly clean up data, especially in scratch.
- Unused files that have to be kept should be moved off-system.
Quotas
On our cluster, each user has access to the /global/home and /global/scratch spaces by default and each group has access to project space in /global/project. These areas are subject to disk quota
| Area | Quota | Backup ? | Purge ? | Default ? | On Nodes? |
|---|---|---|---|---|---|
| /global/home | 1 TB | Yes | No | Yes | Yes |
| /global/scratch | 5 TB | No | Yes | Yes | Yes |
| /global/project | 3 TB | Yes | No | Yes | Yes |
| /local | 1 TB | No | Yes | No | No |
