Partition Table (Cylinder boundaries) and lost space
Hello.
I didn't find anything in search so i am asking. I have a doubt if this is the proper forum or hardware forum but i think itisn't pure hardware question. My question is why should a partition end on a cylinder boundary when Linux doesn't use CHS (I don't care about compatibility with windows). Let me mention an example. I have a 80GB sata disk. "SCSI device sdb: 156250000 512-byte hdwr sectors (80000 MB)" It has 156,250,000 sectors. When i run fdisk/cfdisk I get the geometry of C9726,H255,S63 which pretty much is the default used by large disks in LBA (H255,S63 and C is total sectors/255/63). This results to 156,248,190 sectors. The first partition starts in 63 sector (due to DOS compatibility that the first head was unused) which is not needed for linux and cfdisk has a maximize command that starts the partition in sector 1. Ok with this. But i can't use the sectors from 156,248,190 and beyond. fdisk let you choose them if you use "sector mode" and not "cylinder mode(default)", but when you run cfdisk or "sfdisk -V" or any other tool you get the message that the partition runs beyond the end of the disk. The sectors that are not used are 1810 which results to 926,720 . I don't ask about the wasted space which is 1M but just why this is happening. the fdisk manual mentions: Code:
In a DOS type partition table the starting offset and the size of each Am i right ? Is there a way to use all the sectors ? I tried to use a different geometry when creating the partition table. I used C12500,H250,S50 and it works. I can get all the sectors, but "sfdisk -l /dev/sdb" mentions: Code:
Disk /dev/sdb: 9726 cylinders, 255 heads, 63 sectors/track shouldn't matter but i ask in order to be sure i don't break anything. Thank you for your time. |
Since you're not going to run another OS than Linux, you should have no problems (without guarantee).
If you want to avoid the wasted sectors, you could manually edit the partition data on disk (Don't do it! I've done it once (for other reasons), and it worked, but 1 MB is not worth the effort). |
Quote:
partition tool. It is not about the 1MB.I asked to know why this is happening. Thank you for replying. |
I guess the reason is: to stay backwards compatible. But maybe nowerdays it would be better to make the standard behaviour of partition programs to not align the partition to some antique boundaries, or at least provide an option to avoid the alignment; after all, partitions behind the first couple of physical GB can't be accessed using CHS, so why remain backwards-compatible?
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