eichelbe@nadc.ARPA (09/18/85)
--- >Date: Fri, 13 Sep 85 12:55:02 pdt >From: niel <@CSNET-RELAY.ARPA,@ucsc.csnet (Niel Warren):niel@ucsc.csnet> >To: eichelbe@NADC.ARPA, unix-wizards@BRL.ARPA >Subject: Re: swapon problem > >About that c partition... c accesses the whole disk including >the space reserved bad blocks. > >-Niel > > --- Wizards: Is this really true? Am I playing with fire by having a c partition on a CDC 9766 (like an RM05) controlled by an SI 9400 controller? I'm interested in the c partition part, not in flames about the 9766 or SI. I'm running under VAX 4.1 BSD UNIX. Jon Eichelberger eichelbe@NADC
ron@brl (Ron Natalie) (09/18/85)
Of course it accesses the bad block table. It lets you look at the entire disk. However the sizes in fstab do not overlap the bad block area (or shouldn't) even though you can use this device to read them. Just constrain your newfs to the value in fstab which provides for a file system to span the usuable area of the disk. -Ron
chris@umcp-cs.UUCP (Chris Torek) (09/19/85)
> From: eichelbe@nadc.ARPA >> From: niel <@CSNET-RELAY.ARPA,@ucsc.csnet (Niel Warren):niel@ucsc.csnet> >> >> About that c partition... c accesses the whole disk including >> the space reserved bad blocks. Like all blanket statements, this is false. :-) It depends on how you've set up your partition tables. The distributed 4.1 and 4.2 code does indeed include the bad block areas in the C partition. > Wizards: Is this really true? Am I playing with fire by having > a c partition on a CDC 9766 (like an RM05) controlled by an SI 9400 > controller? Not necessarily. Not only does it depend on your tables, there is nothing that says you must use the entire available area for a file system or swap/paging region. As I recall, unmodified 4.1 demanded that all paging areas be the same size; this size was wired into a variable in the various swap configuration files. Under 4.2 (and modified 4.1) there is a third entry in ``struct swdevt'' which indicates the size of the area. If this third value is zero, the block device's ``dsize'' routine is called during swap configuration to find out how much space is available. This routine typically returns the value from the appropriate partition table. In any case, if you have set your swap size to 600 blocks, then you have 300K of swap space, even though you can access 600000 blocks (300M) via the C partition. (600 blocks is a silly size; this is just an example.) One can also make a file system that is smaller than the available space. This is usually pointless (but consider Sun's network disk for a counterexample). All in all, you are probably better off if you avoid the C partition, unless you have adjusted your tables; if you do not use it, you cannot get into trouble. However, there is nothing inherently wrong with using the area. -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251) UUCP: seismo!umcp-cs!chris CSNet: chris@umcp-cs ARPA: chris@maryland