Introduction to High Performance Computing

To begin this unit, we will introduce the basis of high performance computing (HPC), and the general architecture of HPC systems at TACC. We will cover how to log in to an HPC system, and navigate the different file systems available. After going through this module, students should be able to:

Describe the basic architecture of an HPC system
Log in to an HPC system at TACC
Navigate the different file systems available on TACC HPC systems

Basic HPC System Architecture

As you prepare to use TACC systems for this unit, it is important to understand the basic architecture. Think of an HPC resource as a very large and complicated lab instrument. Users need to learn how to:

Interface with it / push the right buttons (Linux)
Load samples (data)
Run experiments (jobs)
Interpret the results (data analysis / vis)

Tips for Success

Read the documentation.

Learn node schematics, limitations, file systems, rules
Learn about the scheduler, queues, policies
Determine the right resource for the job

User Responsibility on Shared Resources

HPC systems are shared resources. Your jobs and activity on a cluster, if mismanaged, can affect others. TACC staff are always available to help.

Log in to Lonestar6

To log in to Lonestar6, follow the instructions for your operating system below.

Mac / Linux

Open the application ‘Terminal’ and:

[local]$ ssh username@ls6.tacc.utexas.edu

To access the system:

1) If not using ssh-keys, please enter your TACC password at the password prompt
2) At the TACC Token prompt, enter your 6-digit code followed by <return>.

(enter password)
(enter 6-digit token)

Windows (Use WSL2 or an SSH Client)

Open the application WSL2 :

[local]$ ssh username@ls6.tacc.utexas.edu

To access the system:

1) If not using ssh-keys, please enter your TACC password at the password prompt
2) At the TACC Token prompt, enter your 6-digit code followed by <return>.

(enter password)
(enter 6-digit token)

Or open an SSH client like PuTTY:

Open the application 'PuTTY'
enter Host Name: ls6.tacc.utexas.edu
(click 'Open')
(enter username)
(enter password)
(enter 6-digit token)

Successful Login to Lonestar6

If your login was successful, your terminal will look something like this:

Last login: Mon Apr 13 16:09:20 2026 from 129.114.111.41
------------------------------------------------------------------------------
Welcome to the Lonestar6 Supercomputer
Texas Advanced Computing Center, The University of Texas at Austin
------------------------------------------------------------------------------

Unauthorized use/access is prohibited. **
If you log on to this computer system, you acknowledge your awareness
of and concurrence with the UT Austin Acceptable Use Policy. The
University will prosecute violators to the full extent of the law.

TACC Usage Policies:
http://www.tacc.utexas.edu/user-services/usage-policies/
______________________________________________________________________

Welcome to Lonestar6, please read these important system notes:

06/18/2025: /work access has been restored.

--> Lonestar6 user documentation is available at:
https://portal.tacc.utexas.edu/user-guides/lonestar6

---------------------- Project balances for user wallen -----------------------
| Name           Avail SUs     Expires | Name           Avail SUs     Expires |
| TACC-SCI            5933  2026-07-31 | OTH22024           19171  2026-07-31 |
| IBN23016            8000  2027-03-31 | IBN22007            1145  2026-09-30 |
| DrugDiscovery       6025  2026-05-31 | DBS22003             500  2026-09-30 |
| STAR-Avathon        4989  2027-02-28 | OTH24028             525  2029-07-31 |
------------------------- Disk quotas for user wallen -------------------------
| Disk         Usage (GB)     Limit    %Used   File Usage       Limit   %Used |
| /scratch        33955.8       0.0     0.00      1692900           0    0.00 |
| /home1              7.6      10.0    75.91        56672           0    0.00 |
| /work             636.2    1024.0    62.13      2533936     3000000   84.46 |
-------------------------------------------------------------------------------
login1.ls6(1001)$

Note

The welcome message you receive upon successful login to Lonestar6 has useful information for you to keep track of. Especially of note is the breakdown of disk quotas for your account, as you can keep an eye on whether your usage is nearing the determined limit.

Once your usage is nearing the quota, you’ll start to experience issues that will not only impact your own work, but also impact the system for others. For example, if you’re nearing your quota in $WORK, and your job is repeatedly trying (and failing) to write to $WORK, you will stress that file system.

Another useful way to monitor your disk quotas (and TACC project balances) at any time is to execute:

[ls6]$ /usr/local/etc/taccinfo

Tip

Refer back to Linux Essentials if you need a refresher on navigating Linux file systems.

Systems Available at TACC

Clusters

Frontera: The fastest academic supercomputer in the world, providing computational capability that makes larger, more complex research challenges possible.
Vista: Vista expands TACC’s capacity for AI and ensures that the broadscience, engineering, and education research communities have access to the most advanced computing and AI technologies.
Stampede3: The newest strategic resource advancing NSF’s supercomputing ecosystem for the nation’s open science community.
Lonestar6: Supporting Texas researchers in providing simulation, data analysis, visualization, and AI/machine learning.
Jetstream2: A user-friendly, scalable cloud environment with reproducible, sharable computing on geographically isolated clouds.

Storage Systems

Corral: Storage and data management resource designed and optimized to support large-scale collections and a collaborative research environment.
Ranch: Long-term data archiving environment designed, implemented, and supported to provide storage for data sets of the TACC user community.
Stockyard: Global file system at the center of TACC’s system ecosystem that supports data-driven science by providing online storage of large datasets, and offers migration for further data management and archiving.

File Systems

The account-level environment variables $HOME, $WORK, and $SCRATCH store the paths to directories that you own on each of these file systems.

File System	Quota	Key Features
`$HOME`	10GB	Backed up. Recommended Use: scripts and templates, environment settings, compilation, cron jobs
`$WORK`	1TB 3,000,000 files	NOT backed up. Recommended Use: software installations, original datasets that can’t be reproduced.
`$SCRATCH`	No quota assigned	NOT backed up. Recommended Use: Reproducible datasets, I/O files: temporary files, checkpoint/restart files, job output files

Files in $SCRATCH are subject to purge if access time is more than 10 days old.

Navigating File Systems

To navigate the different file systems available on TACC HPC systems, you can use the standard cd command along with the PATH, or you can use some TACC-specific shortcuts:

Home Directory: To change to your home directory, you can use:
```
[ls6]$ cd $HOME
# or
[ls6]$ cd
```
Work Directory: To change to your work directory, you can use:
```
[ls6]$ cd $WORK
# or
[ls6]$ cdw
```

Scratch Directory: To change to your scratch directory, you can use:
```
[ls6]$ cd $SCRATCH
# or
[ls6]$ cds
```