disk slices

disk slices

Post by Heiko Swar » Sat, 17 Jul 1999 04:00:00



Hi Experts,

the Solaris documentation says, that slice 2 of any disk doesn't contain
a filesystem.
It represents the whole disk.
What is the reason for that? I configured a Solaris 2.7 system putting
/usr into slice 2.
It works fine. Is there a risk?

Thanks a lot for your help!

Heiko

 
 
 

disk slices

Post by Chris Thomps » Sat, 17 Jul 1999 04:00:00




Quote:

>the Solaris documentation says, that slice 2 of any disk doesn't contain
>a filesystem.
>It represents the whole disk.
>What is the reason for that?

It's a convention, like using slice 1 for swap. It's not mandatory.

Quote:>                             I configured a Solaris 2.7 system putting
>/usr into slice 2.
>It works fine. Is there a risk?

The risk is someone assuming that they can copy the disk by

  dd if=/dev/rdsk/c*t*d*s2 of=/dev/rdsk/c#t#d#s2 bs=[something big]

without checking first.

On the whole, it's a good idea to stick to the convention unless you have
an urgent need to use all 8 slices.

Chris Thompson
Email: cet1 [at] cam.ac.uk

 
 
 

disk slices

Post by Andrew Gabri » Sun, 18 Jul 1999 04:00:00






>>the Solaris documentation says, that slice 2 of any disk doesn't contain
>>a filesystem.
>>It represents the whole disk.
>>What is the reason for that?

>It's a convention, like using slice 1 for swap. It's not mandatory.

>>                             I configured a Solaris 2.7 system putting
>>/usr into slice 2.
>>It works fine. Is there a risk?

>The risk is someone assuming that they can copy the disk by

>  dd if=/dev/rdsk/c*t*d*s2 of=/dev/rdsk/c#t#d#s2 bs=[something big]

>without checking first.

Another one is that prtvtoc assumes slice 2 is not a real slice
when working out unused space on the disk, so it will report the
space occupied by slice 2 as free.

Quote:>On the whole, it's a good idea to stick to the convention unless you have
>an urgent need to use all 8 slices.

...or all 16 slices on Solaris x86.

--
Andrew Gabriel
Consultant Software Engineer

 
 
 

1. Any equiv to Solaris' disk slices for root fs under AIX?

With Solaris, you can set up a disk slice (eg c0t0d0s1) to hold an
alternative miniroot (basic /, /etc, /tmp, /boot, etc.) for disaster
recovery purposes on the same system disk, so that if the system disk
slice holding the normal root filesystem gets nuked, one can just
direct it to boot off the miniroot's slice via a manual boot command
from the OpenBoot PROM command line.

Is there any equivalent for this in AIX?

The closest I see is the alt_disk_install stuff, but that requires an
entirely separate disk of its own. Same deal with a mirrored setup.

My team and I were wondering about this, being a mixed Solaris and AIX shop.

-Dan

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