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Old 04-21-2008, 02:31 PM
Kai Schaetzl
 
Default fdisk partition table plus sign

What does the plus sign after the blocks value exactly mean in the fdisk
output? Some research reveals that it indicates that not all the blocks
are included in the fdisk value. But what does this exactly mean?

Kai

--
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Old 04-21-2008, 04:06 PM
"William L. Maltby"
 
Default fdisk partition table plus sign

On Mon, 2008-04-21 at 16:31 +0200, Kai Schaetzl wrote:
> What does the plus sign after the blocks value exactly mean in the fdisk
> output? Some research reveals that it indicates that not all the blocks
> are included in the fdisk value. But what does this exactly mean?

IIRC, it means that the partition did not start/end on a cylinder
boundary. I get these all the time when I manually configure partitions
to get every last block used (not since "large" drives were about
500MB).

As to loss, maybe yes. When you allocate using multipliers, (10GB,
100MB, etc.) the bytes per cylinder is used as a divisor. This *may*
leave some part of a cylinder unused at the end. With todays drive
sizes, even anal me doesn't worry about it anymore.

>
> Kai
>

HTH
--
Bill

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Old 04-21-2008, 05:30 PM
Robert Nichols
 
Default fdisk partition table plus sign

Kai Schaetzl wrote:
What does the plus sign after the blocks value exactly mean in the fdisk
output? Some research reveals that it indicates that not all the blocks
are included in the fdisk value. But what does this exactly mean?


Those blocks are 1024 bytes each, so you'll see that "+" when the
partition contains an odd number of 512-byte sectors. That's all
it means. The root cause is that the usual pseudo-geometry used
is 63 sectors/track and 255 heads, which results in a "cylinder"
with an odd number of sectors.

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Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.

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Old 04-21-2008, 05:31 PM
Kai Schaetzl
 
Default fdisk partition table plus sign

William L. Maltby wrote on Mon, 21 Apr 2008 12:06:06 -0400:

> As to loss, maybe yes. When you allocate using multipliers, (10GB,
> 100MB, etc.) the bytes per cylinder is used as a divisor. This *may*
> leave some part of a cylinder unused at the end. With todays drive
> sizes, even anal me doesn't worry about it anymore.

well, I was wondering about that when I wanted to duplicate a partition
and I wasn't able to get exactly the same block size in fdisk, neither
with size in GB nor with last cylinder.

Kai

--
Kai Schätzl, Berlin, Germany
Get your web at Conactive Internet Services: http://www.conactive.com



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Old 04-21-2008, 05:42 PM
"William L. Maltby"
 
Default fdisk partition table plus sign

On Mon, 2008-04-21 at 19:31 +0200, Kai Schaetzl wrote:
> William L. Maltby wrote on Mon, 21 Apr 2008 12:06:06 -0400:
>
> > As to loss, maybe yes. When you allocate using multipliers, (10GB,
> > 100MB, etc.) the bytes per cylinder is used as a divisor. This *may*
> > leave some part of a cylinder unused at the end. With todays drive
> > sizes, even anal me doesn't worry about it anymore.
>
> well, I was wondering about that when I wanted to duplicate a partition
> and I wasn't able to get exactly the same block size in fdisk, neither
> with size in GB nor with last cylinder.

As long as the files system does not map beyond the end of a partition
on the target drive, you'll be OK. If the drive geometry *appears* the
same and your target partition(s) are at leaset as large as the source
partitions, you should be OK.

Given the above, the only ill-effects I've seen are intangible. As when
sfdisk gives you a warning about the geometry appears to have been
created for one C/H/Spt but this drive seems different.

Since we all do LBA now (don't we?), no harm.

If you want to be absolutely sure, "man sfdisk". This will let you have
complete control, even allocating by sector count. It will let you save
a "map" of the current drive and apply it to a new drive.

If you are fairly new to this level of stuff (... hmm, even if not),
please have good backup/recovery plans and data if you are affecting
production drives.

>
> Kai
>

HTH
--
Bill

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Old 04-22-2008, 12:32 PM
Kai Schaetzl
 
Default fdisk partition table plus sign

thanks for the explanations, folks!

Kai

--
Kai Schätzl, Berlin, Germany
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