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Feature #2949

format(1m) should make megabyte-aligned partitions

Added by Gordon Ross about 8 years ago. Updated 8 months ago.

Status:
In Progress
Priority:
Normal
Assignee:
Category:
-
Start date:
2012-06-30
Due date:
% Done:

0%

Estimated time:
Difficulty:
Medium
Tags:
needs-triage
Gerrit CR:

Description

Most operating systems no longer attempt to use drive geometry when setting partition boundaries, and instead simply make them megabyte-aligned.
This issue proposes make megabyte-aligned partitions the default, and provide an option (-c) to get the old cylinder-aligned behavior.

Man page addition:

    -c
                          Cylinder alignment.   Make  new  parti-
                          tions  aligned  on cylinders, according
                          to the geometry reported by the device,
                          as  was  common  practice long ago.  By
                          default, format uses the modern conven-
                          tion of aligning partitions on megabyte
                          boundaries.

Just for history, an earlier proposal was:

    -a
                          Align new partitions to 1MB boundaries (default)
    -A
                          Align new  partitions on cylinders, according
                          to the geometry reported by the device,
                          Note that for modern devices that geometry
                          is entirely fictional and can result in partitions
                          that can cause all I/O to be mis-aligned.

History

#1

Updated by Gordon Ross about 8 years ago

  • Subject changed from format(1m) should support megabyte-aligned partitions to format(1m) should make megabyte-aligned partitions

Replaced proposed -a option with a -c option having the opposite sense.

#2

Updated by Gordon Ross 8 months ago

  • Description updated (diff)
#3

Updated by Gordon Ross 8 months ago

  • Description updated (diff)
#4

Updated by Gordon Ross 8 months ago

  • Description updated (diff)
#5

Updated by Gordon Ross 8 months ago

Capturing some email discussion from June 2012 (summarizing)

GWR:
Please review:
2949 format(1m) should support megabyte-aligned partitions
http://www.yalms.org/cr/illumos-2949/

Garrett D'Amore:
Suggests -a / -A and default to megabyte aligned now (-a)

Richard Elling:
Make -a the default now

GWR:
Suggests -c for "cylinder alignment"

Josef 'Jeff' Sipek
review comments / suggestions

Rich Lowe
Would be nice if cmlb did not diverge from the other places that know about this.
(Fixing that may require some more work.)

You can see the email thread on topicbox:
https://illumos.topicbox.com/groups/developer/T25e912f21a7abec7-M3bdf2444fe44b189d01a4330/code-review-2949-format1m-should-support-megabyte-aligned-partitions

#6

Updated by Gordon Ross 8 months ago

  • Status changed from New to In Progress
  • Description updated (diff)

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