Vinum Offset for Swap: 265 or 281?

[Greg 'groggy' Lehey]

On Wednesday, 22 October 2003 at  0:52:35 -0700, rtjohan at syspres.com wrote:
>
>>> So, my understanding of the bsdlabel process seemed correct:
>>> 1) modify swap partition size to be 281 less than what sysinstall
>>> created the partition as
>>> 2) have the swap offset at 281 instead of 0
>>> 3) add vinum partition set to the size of "c" minus 16
>>> 4) have vinum partition offset at 16
>>
>> Yes, that's about it, making a lot of assumptions which you don't
>> mention here.  For the full story, see
>> http://www.vinumvm.org/cfbsd/vinum.pdf.
>
> bsdlabel part is clear.

This statement isn't clear to me.

> vinum create file - why driveoffset different then partition offset?

Which partition?

> In particular, looking at the bottom of page 238 of your document -
> the driveoffset values for a subdisk are 16 less then the offset of
> the partition it's mapping.

Yes, of course.  The Vinum drive starts 16 sectors later.

> For instance you have partition "e" with size=3142987 and offset
> 5242880, but the var volume uses sd len 3142987s driveoffset 524864s
> drive rootdev. Why is it necessary for each subdisk to be 16 lower
> then the partition it will be mapping?

Take /var for example.  It's on partition e, which starts at offset
5242880 from the beginning of the disk.  The subdisk starts at offset
5242864 from the beginning of the drive.  The drive starts at offset
16 from the beginning of the disk, so the subdisk starts at 5242880
from the beginning of the disk.

>>> 2) The subdisk offset is = (partition offset - 16)
>>
>> No.
>
> Seems to me that's what's going on on page 238.

Depends on which partition you're talking about.

Greg
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