Use of 3rd partition when entire disk is raw.

Use of 3rd partition when entire disk is raw.

Post by Anthony Mandi » Wed, 24 Apr 1996 04:00:00



Whats the story with the C partition or partition 2 (depending
        on the flavour of Unix) when the entire disk is used as a raw
        device.

        I know that by convention, the 3rd partition represents the
        whole disk. While this would be useful in quite a few cases,
        when using the disk as a raw device (as with a database) and
        you are trying to squeeze the maximum number of partitions
        out of the disk, 8 would be preferable to 7. Could the 3rd
        partition be treated as normal? Is it just an issue with format
        or is the convention more ingrained than that?

        Thank you for tolerating this interuption to your normal flame
        reading. I now return you to the normal rubbish.

-am

 
 
 

Use of 3rd partition when entire disk is raw.

Post by Neal P. Murp » Wed, 24 Apr 1996 04:00:00



>Whats the story with the C partition or partition 2 (depending
>    on the flavour of Unix) when the entire disk is used as a raw
>    device.
>    I know that by convention, the 3rd partition represents the
>    whole disk. While this would be useful in quite a few cases,
>    when using the disk as a raw device (as with a database) and
>    you are trying to squeeze the maximum number of partitions
>    out of the disk, 8 would be preferable to 7. Could the 3rd
>    partition be treated as normal? Is it just an issue with format
>    or is the convention more ingrained than that?

The convention is that partition 'C' or '2' or slice '7' is the
whole disk - always the whole disk. The OS needs the whole disk
to be able to write to disk areas outside the usual filesystem/
partition space. For example, Moto's SysV R3x writes the slice table
(as well as bootstrap, label and other info) on the disk before the
slices begin.

Some OSen allow one to make a file system smaller than the entire
partition, so that, for instance, one could use a 500MB slice as
a 200MB file system and leave 300MB for raw access. Provided any
program accessing the raw area *always* start after the filesystem,
the filesystem would remain healthy.

If you need more than 7 partitions or slices, you *might* need a new
OS. :(

Quote:>    Thank you for tolerating this interuption to your normal flame
>    reading. I now return you to the normal rubbish.

The pleasure is yours, I'm sure. :)

Fest3er
--
The Microsoft thirty bladed swiss army knife with corkscrew and magnifying lens
[is] inappropriate for all of my word processing needs.

  - Stephanie Evans

 
 
 

1. 5.7 'df' on first partition reporting the entire disk?

I am experiencing something odd on an Ultra60 Solaris 7 box that I've
just taken over.  There are several 9GB SCSI drives on the system, and
some are partitioned in half.  Each half gets its own ufs filesystem
and gets mounted; nothing wild, everything's fine.

I noticed that one drive was only getting its second half used, so I
mounted the first half temporarily to see if there was anything on it.
The partition mounted as a ufs filesystem, no errors.

However, a 'df' reports that partition having nearly 9GB free, when it
should only have 4.5.  Even the other half has a significant amount of
space taken up.

Here is the output from prtvtoc showing the partition table (exactly
like the other drives), then a couple of df's, including a df on the
"entire drive" slice.

   # prtvtoc /dev/rdsk/c1t9d0s0
   * /dev/rdsk/c1t9d0s0 partition map
   *
   * Dimensions:
   *     512 bytes/sector
   *     133 sectors/track
   *      27 tracks/cylinder
   *    3591 sectors/cylinder
   *    4926 cylinders
   *    4924 accessible cylinders
   *
   * Flags:
   *   1: unmountable
   *  10: read-only
   *
   *                          First     Sector    Last
   * Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
          2      5    01          0  17682084  17682083
          5      0    00          0   8841042   8841041   /mnt
          6      4    00    8841042   8841042  17682083   /usr/local
   # df /usr/local /mnt
   /usr/local         (/dev/dsk/c1t9d0s6 ): 7697234 blocks   505800 files
   /mnt               (/dev/dsk/c1t9d0s5 ):17407392 blocks  1044732 files
   # df -k /usr/local /mnt
   Filesystem            kbytes    used   avail capacity  Mounted on
   /dev/dsk/c1t9d0s6    4352742  504125 3805090    12%    /usr/local
   /dev/dsk/c1t9d0s5    8703705       9 8616659     1%    /mnt
   #
   # df -k /dev/dsk/c1t9d0s2
   Filesystem            kbytes    used   avail capacity  Mounted on
   /dev/dsk/c1t9d0s2    8703705       9 8616654     0%    

Could somebody tell me whether this is a df bug, a hardware problem, or
just utter stupidity on my part?  What am I missing here?

Much thanks,
Phil

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