farrell@pangea.Stanford.EDU (Phil Farrell) (05/03/91)
In article <JTKOHL.91May1105340@quicksilver.MIT.EDU> jtkohl@MIT.EDU (John T Kohl) writes: >In article <1005@aerodec.anu.edu.au> tridge@aerodec.anu.edu.au (Andrew Tridgell) writes: > >> Basically my questions to the net are : > >> - what caused the problem in the first case > >The symptoms you describe exactly match my experience from about 5 years >ago with a 4.2BSD filesystem. > >The 4.xBSD fsck wants to read its disk blocks in groups of 4. The >partition size you have (by default, unfortunately) is not a multiple of >four. When reading the last two blocks, fsck gets a short read and gets >confused. > >John Kohl <jtkohl@MIT.EDU> This brings up the issue of why Digital Equipment insists upon shipping systems with unreasonable default disk partitioning. I NEVER use the default partitions from DEC - if nothing else, they are never optimized to be on cylinder group boundaries, as newfs would like, so they often end up wasting space - as much as a megabyte on a large partition. Now we hear of a more subtle problem with DECs default partitionings. I would like DEC to expend a little energy to carefully design its default disk partitions (both in the superblock (chpt) and in /etc/disktab) so they fall on cylinder group boundaries. Meanwhile, you can do it yourself. Just remember that newfs wants to put 16 cylinders in a group, and using the geometry information from /etc/disktab, compute disk partition boundaries that fall on integral cylinder group boundaries. Use chpt to change the on-disk partition table to these more efficient boundaries on your new disks (it will wipe out anything already on the disk). For your system disk, when you boot the Ultrix installation tape, choose the "System Management" option instead of Basic or Advanced installation, and you will get a "mini" UNIX with a Bourne shell and access to a few basic commands, including /etc/chpt. You can then repartition your system disk, reboot the installation tape, and do an Advanced Installation to use your new custom partitions. -Phil Farrell, Computer Systems Manager Stanford University School of Earth Sciences farrell@pangea.stanford.edu
tridge@anu.oz.au (Andrew Tridgell) (05/03/91)
I've now fixed the problem and have given back the loaned disk (It felt good having 1.2Gb but it couldn't last :-) I heartily agree with the poster who said that DEC should supply the disk with sensible partition tables and disktab entries. It is very sloppy to bung in any old partition entries without considerable thought as to the consequences. What I finally did was to chpt the old disk to reduce the g pattition to a multiple of four, then a newfs and a dump/restore from the new (loaned) disk. fsck is now happy with our file system, so I can finally do things remotely. I'm also very glad someone could give me a logical explanation of the problem (MANY thanks to John Kohl), so I can rest in peace, knowing ( I hope :-) ) that it isn't going to jump on me again when I move some more files. Thanks to everyone who took the time to reply, the help was much appreciated. (and thanks to DEC for the loan of the disk - doing all this via tape would have been a real pain) Andrew -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Andrew Tridgell CSLab, Research School of Physical Science tridge@aerodec.anu.edu.au Australian National University =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
paul@caen.engin.umich.edu (Paul Killey) (05/06/91)
Someone, writes >The symptoms you describe exactly match my experience from about 5 years >ago with a 4.2BSD filesystem. In many respects, using Ultrix requires a trip in the wayback machine and some recollection about what was the case in 1985.