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From: | Chris Johnson |
Subject: | bug#22497: parted math - Q2 and Q3 ? |
Date: | Sat, 30 Jan 2016 17:03:49 -0500 |
User-agent: | Mozilla/5.0 (X11; SunOS i86pc; rv:10.0.6esrpre) Gecko/20120731 Thunderbird/10.0.6 |
# parted
/dev/rdsk/c7t1d0p0 GNU Parted 2.3.0 Using /dev/rdsk/c7t1d0p0 Welcome to GNU Parted! Type 'help' to view a list of commands. (parted) unit cyl unit cyl (parted) p p Model: Generic Ide (ide) Disk /dev/rdsk/c7t1d0p0: 121601cyl Sector size (logical/physical): 512B/512B BIOS cylinder,head,sector geometry: 121601,255,63. Each cylinder is 8225kB. Partition Table: gpt Number Start End Size File system Name Flags 1 0cyl 121600cyl 121600cyl zfs 9 121600cyl 121601cyl 1cyl Question 2) Based on the parted information shown above, I would assume that the Total Sectors could be calculated thus: 121601 * 255 * 63 = 1953520065 Indeed, gparted shows this value when you look at the disk device information. Alas, when I switch to units of sectors I get a different value!!! (parted) unit s unit s (parted) p p Model: Generic Ide (ide) Disk /dev/rdsk/c7t1d0p0: 1953525168s <--------- Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 256s 1953508750s 1953508495s zfs 9 1953508751s 1953525134s 16384s Question 3) When I look at the information above where units are sectors, it is clear that the "End" sector number is the last sector being used in the partition. This is supported in the above example by the fact that partition 9's first sector number is one higher than the End sector number of partition 1. Alas, when looking at the information in units of cylinders, it seems like there is a change in meaning. Number Start End Size File system Name Flags 1 0cyl 121600cyl 121600cyl zfs 9 121600cyl 121601cyl 1cyl If there are 121600 cylinders in partition 1 and the first of those is cylinder number 0, I would expect the ENDing cylinder number to be 121599. This expectation would also seem reasonable given that the starting cylinder number for partition 9 is 121600. Hmmm, perhaps what I am looking at is how parted displays information when partitions are not sized to end on a cylinder boundary? It likely is the case that partition 1 does not nicely end with the last sector of cylinder 121599 but instead has some sectors in cylinder 121600 and furthermore that partition 9's starting sector is also in cylinder 121600 ... Is that what's going on here? Given that this drive is SSD and the whole cylinder,head,sector thing is all a mirage, I assume there is no value to trying to align the partitions to cylinder boundaries. Thanks for your insight. |
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