Last Updated: 15 Sep 2015

Resource use in the labs is governed by efficient management of shared resources such as file space, network capacity, and printing.

File Space Background

File space for home directories resides on a central storage server's local disks. It is designed to be:

• robust

  ZFS checks for raw disk block integrity and was configured to use software RAID to allow for continued (degraded) operation despite the failure of one of the disk drives, until the failed disk is replaced.

• secure

  Default file access permissions prevent non-authorized viewing and changing of directory contents.

• clean

  Anti-virus software checks all files for known virii.

• recoverable

  Daily backups are performed to allow for recovery after system failure and occasional deletions of files at least a day old.

• accessible

  The home directory is tied to each student's login, not the computer on which they are working on, enabling access from any capable local workstation, and, with an additional server, secure remote access from any other computer supporting the SSH protocol.

Network Capacity Background

We use an Ethernet network, and will soon be part of a wireless network (which is not really Ethernet, though it works through the ether -- go figure!).

In all labs, computers are connected via copper cables to a switch, which is connected by a copper cable to a wall jack. In all buildings except Cherry-Parkes, the wall is the demarcation point for the Information Technology department at UW Seattle -- "UW IT".

The demarcation point is the transition point where the responsibility changes from one group of people (viz., our department) to another (UW IT). UW IT manages the network infrastructure within UWT buildings (but not within rooms), between buildings and between UWT and UW Seattle. This is the way it is and is likely to be until we (as a campus) have a need to change it and want to spend money to do so (e.g., hiring someone to be the network guru and to monitor the network).

As an aside, this is why we chose to route all networking to our communications room in Cherry-Parkes: we gain control of the jacks. This control:

1. prevents students from intentionally or inadvertently connecting to the Internet -- all access is controlled as the course demands
2. allows us to connect labs using whatever equipment we want
3. allows for fiber connections to the labs
4. allows for easier routing and firewalling
5. protects the network from being affected by student mistakes in networking or lack of computer security

Current (15 Sep 2015) capacity is at least 1 Gb between Tacoma and Seattle, 1Gb/sec fiber between buildings, 1Gb/sec copper within buildings.

Please note that these are bits, not bytes, so the maximum data transfer within a building is 100 MB/sec -- if no one else is using the ethernet. Add in collisions, and on a well-managed network you can probably get closer to 80MB/sec max during a busy day.

Impact of Assignments and Projects

Course assignments may impact the efficiency of this centralized file space and the network. For example, files with megabytes of data will take a long time to download from a faculty.washington.edu web site. If the student puts it on the home directory, it will take even longer, since it needs to come to that student's computer first, then get written to the centralized file space. That's twice the network bandwidth, although our internal network works much faster than the current connection to Seattle.

When you consider that many students will do the same thing -- that's a lot of network traffic and disk space consumption for the same file.

Our recommendation is that large files (larger than 100MB) that are read-only and not used for performance measurements be placed in one readable location on our local, centralized file space. That could be a directory you make available from your lab account, or one you request lab staff to make. That addresses the disk space issue with a shared file, but not the network access.

Sometimes, a student is asked to generate their own large data files, which they normally do on their home directory because it is convenient and it roams with them. However, to minimize disk space and since the files are fairly temporary and easily regenerated, it would be preferable to use the computer's local hard disk for such work (specifically, the C:\temp directory).

Anytime you ask them to measure the performance, it should be done using the local computer. That means that the data files should reside on the local computer (in the C:\temp directory). That will keep network effects and disk space contention out of their timings.

Printing

Paper and toner cartridges are expensive. It costs a lot less to have the Copy Center print your handouts and assignments that for the students to print them out in the labs.

Please refer your students to this information: How to Conserve Paper and Toner.

Change Log

15 Sep 2015	Updated links and network information
8 Nov 2002	Original document