shollen%odin.Wright.EDU@relay.cs.net (Sheila Hollenbaugh) (12/09/88)
In v5n28, Keith F. Lynch describes file system trashing problems on a SUN-3/260, and quotes his Sun rep. as saying that this situation is "normal" when the disk partition is more than 90% full and when processes try to use too much memory. Since he asked that replies be sent via email, there were no followup postings. Recently we have been having problems that sound very similar, and on _two_ systems, a SUN-3/280 and Sun-3/180, each with two Fujitsu Eagles. I would appreciate hearing from anyone who has insight into this problem. If you reply via email, I'll be glad to post a summary. Many thanks! Sheila Hollenbaugh Wright State University Research Center CSNET: shollen@SPOTS.Wright.Edu 3171 Research Blvd., Kettering, OH 45420 UUCP: ...!wright!shollen (513) 259-1382
frank@morgan.com (Frank Wortner) (12/20/88)
shollen%odin.Wright.EDU@relay.cs.net (Sheila Hollenbaugh) writes: >In v5n28, Keith F. Lynch describes file system trashing problems on a >SUN-3/260, and quotes his Sun rep. as saying that this situation is >"normal" when the disk partition is more than 90% full and when processes >try to use too much memory. "Normal?!?" I sure hope not! Let's hope this was just a case of misprounciation. "Thrashing" can occur if the filesystem gets too full. The worst symptom in this case should be unaccepably slow performance as the disk drive seeks wildly in an attempt to use what few free bocks exist. BSD "fast" filesystem implementations usually reserve the last 10% of available space just to insure that this does not happen. "Trashing" should *never* occur under any circumstances---in theory. ;-) [[ Understand what Frank means by "reserve the last 10%". The percentage capacity figure in the output of a "df" hides the last 10% of the disk. When that column says "100%" full, the disk is really only 90% full. The kernel also prevents non-root users from writing to the disk when it is that full. This is why you will sometimes see disks at "106%" full. That means that root continued to fill it up after it reached "100%". Although I feel that the motivation was wrong (they did it because the so-called "fast file system" thrashed above 90% capacity), the idea of having a small percentage reserved for root-only access is nice. --wnl ]] Frank