mario%research7.computer-science.manchester.ac.uk@nss.cs.ucl.ac.uk (Mario Wolczko) (02/23/89)
A few days ago a good part of 1 cylinder of our Super Eagle became defective. The SUN service-person who dealt with the problem added some sectors to the drive's defect list, and mapped others on to "spare" sectors. The entire cylinder came from a client swap area (SunOS 4.0 swap file), so we didn't lose any data. However, after the fix, the client ran very unpredictably, with periods of 10-20 seconds when apparently no useful work was taking place (the display would freeze). These coincided with periods of high load (4-8) on the server. Thankfully, there was enough free space in the client swap partition for me to make a new swap file, remove the old one, and create smallish (256Kb) files until one covered the defective cylinder. After this, the client behaved normally again. That something strange is happening is indicated by the following: mushroom# cd /export/swap mushroom# ls -l crud* -rw------t 1 root 256000 Feb 17 18:07 crud1 -rw------t 1 root 256000 Feb 17 20:09 crud2 mushroom# /bin/time dd bs=8192 if=crud1 of=/dev/null 31+1 records in 31+1 records out 24.0 real 0.0 user 0.3 sys mushroom# /bin/time dd bs=8192 if=crud2 of=/dev/null 31+1 records in 31+1 records out 0.2 real 0.0 user 0.2 sys Note the enormous amount of real time to read "crud1" (which contains the defective cylinder) compared to a "normal" file. It is accompanied by the noise of a Super Eagle trying to break out of its mounting (flee the nest? :-) as its heads bounce from one side of the disk to the other. My question is: how can I find out which sectors have been remapped? "format" will print out the defect list for me, but I can't find anything in the manuals about mapping sectors to other areas (appropriate RTFM welcome). I shudder to think what the system would be like if, say "ls" contained one of these sectors... Mario Wolczko Dept. of Computer Science Internet: mario@ux.cs.man.ac.uk The University USENET: mcvax!ukc!man.cs.ux!mario Manchester M13 9PL JANET: mario@uk.ac.man.cs.ux U.K. Tel: +44-61-275 6146 (FAX: 6280)