DMS Latency and Related Problems
DMS Latency and Related Problems
DMS Latency and Related Problems
"Latency" as used here refers to the noticeable time lag between an interactive action at a computer console and the visual effects of that action. An example is the typing of characters on the command line without the characters being immediately visible.
During the last several years, DMS faculty have from time to time reported instances of latency. Most of these reports concern latencies when the user is somewhere in their AFS login directory.
Possible causes of latency :
First : Check http://my.njit.edu DMS for notices of outages that may be related to the problem.
Second : Use the following table to try to troubleshoot the problem.
Symptom | Try this test | Comment |
---|---|---|
Latency in a directory (usually your login directory) | Does latency also exist in : /afs/cad/commom/temp/{A, B, C, D}? | If latency does not exist in at least one of these directories, the probable cause is a fileserver(s) or SAN problem. See Note 1. |
Does the same latency also exist on a mathsun ? (This test is to determine if the problem is with your computer). |
If yes, the cause is not your computer. If no, the cause is your computer, or your network connection. Check the load on your computer using top. |
|
Does the same latency also exist via a remote login from your computer to a computer in GITC - e.g., afs<n> ? (This test largely eliminates the factor of the network from GITC to computers in Cullimore). |
If yes, the cause is probably a fileserver or SAN problem. If no, the cause is either the network between GITC and your computer, or your computer. |
|
Does the same latency also exist via a local login to a computer in GITC - e.g. afs<n> ? (This test eliminates the factor of the network from GITC to computers in Cullimore). |
If yes, the cause is a fileserver or SAN problem. If no, the cause is either the network between GITC and your computer, or your computer. |
|
System response : "afs: Waiting for busy volume XYZ .." | None | Volume is being backed up or moved. See Note 2. |
Browser response for URL is slow, or stalls | Try lynx -dump <URL> on other machines, to see if the problem is isolated to your machine/network connection. Try the URLs http://www.njit.edu to test inside NJIT, and http://google.com to test outside NJIT. |
Use process of elimination to determine if the problem is general, or specific to Cullimore, or specific to your computer/network connection. If the same problem exists generally, there is a network problem, or a problem at the target URL. |
Symptom | Try this test | Comment |
Notes :