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
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
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
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
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.
thanks for the explanations, folks!
Kai
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Kai Schaetzl -
Robert Nichols -
William L. Maltby