Re: Why are my boxes sooo slow sometimes? (w/ detailed 'Monitor' output)

SRC wrote: > > ross@charlie.ece.sc.edu > Richard Ross writes: > > I've got a few RISC 6k (520) running AIX 3.2.5 networked > together. At night at ~7pm things slow to a crawl. I get > NFS server 'image' not responding on a machine w/ a few of > 'images' drives mounted (tabletop). Also 'ls' seems > to work fine but when I use 'ls -al' it take several minutes > to come back.(what is the difference?). This happens on 'tabletop' > (the main box) and 'image' (legacy names). > Pings from image to tabletop comes back in 1ms no problem. > What could make this happen like clockwork when there is > no big cron job occuring? An informix backup is running but > has been going for several hours w/ no noticable drag on the > system and when it finishes I still have the problem. > What else should I be looking at? > Below is detailed output from the 'Monitor' utility > > Hi Richard, I don't know much about your file system and your machine. But what I know is the difference between an "ls" and an "ls -al". The ordinary "ls" command doesn't have to read the I-Node table. It just reads the directory file and there is no need to position on the disks. If you start "ls -l" you must read all the I-Node informations and therefore your disk will have to position between the upper I-Node Table and the Data Blocks below. Depending on the size of your filesystems, it may take a very long time using "ls -l". But I think the I-Nodes must reside in the filesystem's cache buffer. Maybe your filesystem cache is too small ? Reading 20MB of your disk in sequential mode would take about 5 to 10 seconds. Reading the same amount of data with positioning would take about 2 minutes. Perhaps this helps, Stefan. stefan@weideneder.de PS: When you found the solution, please send a short reply. I'm very interested in solving performance problems.