Mass Storage – Common FAQs

What is Mass Storage?

Mass Storage services are available for the long-term archiving of important research data files that will be accessed infrequently. If you are interested in backing up your hard drive, you should use the PC backup software provided by UNC instead. Only faculty, staff and graduate students may use the Mass Storage service.

How do I get access to Mass Storage service?

Only faculty, staff, and graduate students may subscribe to the Mass Storage tape archival service.  Be sure to read and understand the intended use of the Mass Storage system, the Appropriate Use Policy and Things to Avoid before subscribing to tape archival service.

You can subscribe to Mass Storage services from the Onyen Services web page. Select Subscribe to Services and then click on Research Computing servers (ie Kure or KillDevil) button.  After some time, A link to a mass storage directory, ms/, will be created in your Research Computing home directory (/nas02/home).   You can then access that directory from many of the Research Computing servers.      Access from the ISIS (isis.unc.edu) general purpose login nodes and AFS home user space will provided upon request by emailing research@unc.edu.

Is there a limit for Mass Storage?

Yes.  Mass Storage is limited; if you will be storing more than 500 Gigabytes of data, you will need to contact Research Computing group ( research@unc.edu ) to arrange to purchase tapes for your data.  For more information, please see “More on Mass Storage” line below.

Why can’t I open my files put on Mass Storage?

When you open a file in your ~/ms directory that has not been used for a while it may appear your task is hung.

Here is the reason.  The data is not in the disk cache.  The Mass Storage system is working to bring all the data on line from tape to disk.  Some clients keep silent about it, some may display a message such as “File temporarily unavailable on the server, retrying…”.

Here is what you need to do.  Do nothing.  Your process will resume once the data is available; usually a few minutes depending on size of the data.

If you want to avoid the warning messages, you can run the command “stage filename”, and wait for 2 minutes before using the file.  This “stage” command can only be run on the Research Computing server login nodes.  The “stage” command will not work on the ISIS login nodes.

How do I determine my disk usage on Mass Storage?

As mentioned previously, the amount of disk space available to users on Mass Storage is limited. In order to calculate current disk space usage, the “sdu” command can be used.  After switching to the ~/ms directory, entering “sdu” at the prompt will provide a listing of all disk usage for individual files and the total disk usage.  The “sdu” command will list total disk space usage on both the StorNext disk cache and in tape storage.  In contrast, the more common “du” command will only list information about files on disk cache and not in tape storage. The “sdu” command has access to metadata with regards to files on tape backup that is not available to the “du” command.  Use of the “sdu –h” command will produce output in a more easily readable format. These commands can only be run on the Research Computing server login nodes.  The commands will not work on the ISIS login nodes.

Additional help

More on Mass Storage

Research Computing home page