GNU bug report logs -
#22497
parted math - Q2 and Q3 ?
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Reported by: Chris Johnson <cj <at> tothemax.us>
Date: Sat, 30 Jan 2016 22:48:03 UTC
Severity: normal
Done: Phil Susi <psusi <at> ubuntu.com>
Bug is archived. No further changes may be made.
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Your message dated Mon, 8 Feb 2016 08:56:06 -0500
with message-id <56B89E76.3000708 <at> ubuntu.com>
and subject line Re: bug#22497: parted math - Q2 and Q3 ?
has caused the debbugs.gnu.org bug report #22497,
regarding parted math - Q2 and Q3 ?
to be marked as done.
(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)
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22497: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=22497
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# 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, *g*parted 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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On 1/30/2016 5:03 PM, Chris Johnson wrote:
> 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.
Yes. The bottom line is: don't use cylinder mode. It is a 30 year old
anachronism that is now just a lie with no basis in reality.
This bug report was last modified 9 years and 165 days ago.
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