This page presents a list of Frequently Asked Questions (and answers) about using the HPC cluster system at the University of Iowa.
| Table of Contents |
|---|
Why is my home account full even after I delete data from it?
This occurs because the cluster utilizes snapshots of your home account to provide protection against accidental deletion or corruption, but this means that data isn't actually removed when you delete a file.
| Info |
|---|
Note that snapshots are not backups as they will expire. |
The snapshots are not an issue for most users but can become problematic if you are running an application that writes and deletes a lot of data from your home account. There are few different potential solutions to this problem.
...
Another option if a scratch volume does not work for your job for some reason is to use /localscratch which is the local hard drive of a compute node. This will likely also be faster than your home account and does not have snapshot backups. Note: This will only work if the data does not need to be available to multiple nodes at once.
...
If none of the above are viable the sysadmin team can turn off snapshots completely on your home account.
| Warning |
|---|
This means that accidental deletion or corruption of files WILL NOT be recoverable by the sysadmin team! |
How do I access snapshots of my home account?
...
How do I access snapshots of my home account?
Snapshots are available as read-only directories in ~/.zfs/snapshot, each representing the state of your home directory at the time the snapshot was created. To restore a file or directory, use the cp command to copy it from a snapshot directory under the snapshot folder to a writable location in your home account (or elsewhere if you prefer). Here is an example of what you might expect to see during the restore process.:
| No Format | ||
|---|---|---|
| ||
[brogers@login-0-1:~]$ cd ~/.zfs/snapshot [brogers@login-0-1:snapshot]$ ls zfs-auto-snap.daily-2011-02-10-00.00 zfs-auto-snap.monthly-2010-10-25-08.58 zfs-auto-snap.weekly-2011-01-22-00.00 zfs-auto-snap.daily-2011-02-11-00.00 zfs-auto-snap.monthly-2010-11-01-00.00 zfs-auto-snap.weekly-2011-01-29-00.00 zfs-auto-snap.daily-2011-02-12-00.00 zfs-auto-snap.monthly-2010-12-01-00.00 zfs-auto-snap.weekly-2011-02-01-00.00 zfs-auto-snap.hourly-2011-02-11-16.00 zfs-auto-snap.monthly-2011-01-01-00.00 zfs-auto-snap.weekly-2011-02-08-00.00 zfs-auto-snap.hourly-2011-02-11-20.00 zfs-auto-snap.monthly-2011-02-01-00.00 zfs-auto-snap.hourly-2011-02-12-00.00 zfs-auto-snap.weekly-2011-01-15-00.00 [brogers@login-0-1:snapshot]$ cd zfs-auto-snap.monthly-2011-01-01-00.00/ [brogers@login-0-1:zfs-auto-snap.monthly-2011-01-01-00.00]$ cp computeilos ~/ |
...