GNU bug report logs - #41577
automatic alignment

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Harald Dunkel <harald.dunkel <at> aixigo.com>
To: bug-parted <at> gnu.org
Subject: automatic alignment
Date: Thu, 28 May 2020 15:00:43 +0200

Hi folks,

Finding a good alignment appears to be a pretty complex task, esp.
for some RAID devices, so I wonder if this could be better supported
in parted? The current

[bzzzzzzzz] The resulting partition is not properly aligned for best performance.

for all 2**n is *more* than annoying. For my lsi RAID I had to use

Number  Start  End           Size          File system  Name    Flags
 1      1536s  46880782847s  46880781312s               export

following the guidelines on [1].

Obviously the align-check option has some deeper knowledge about
a good alignment, but it doesn't tell. :-(


Regards
Harri
[1] https://bdoga.com/how-to-fix-warning-device-is-not-properly-aligned-with-parted/

Message #10 received at 41577-close <at> debbugs.gnu.org (full text, mbox):

From: "Brian C. Lane" <bcl <at> redhat.com>
To: Harald Dunkel <harald.dunkel <at> aixigo.com>
Cc: 41577-close <at> debbugs.gnu.org
Subject: Re: bug#41577: automatic alignment
Date: Thu, 28 May 2020 16:57:32 -0700

On Thu, May 28, 2020 at 03:00:43PM +0200, Harald Dunkel wrote:
> Hi folks,
> 
> Finding a good alignment appears to be a pretty complex task, esp.
> for some RAID devices, so I wonder if this could be better supported
> in parted? The current
> 
> [bzzzzzzzz] The resulting partition is not properly aligned for best performance.
> 
> for all 2**n is *more* than annoying. For my lsi RAID I had to use
> 
> Number  Start  End           Size          File system  Name    Flags
>  1      1536s  46880782847s  46880781312s               export
> 
> following the guidelines on [1].
> 
> Obviously the align-check option has some deeper knowledge about
> a good alignment, but it doesn't tell. :-(

Yeah, it's complicated :) But if you use the latest parted it will tell
you more if you try to create a mis-aligned partition:

Start? 8s
End? 100%
Warning: You requested a partition from 4096B to 1074MB (sectors 8..2097151).
The closest location we can manage is 17.4kB to 1074MB (sectors 34..2097118).
Is this still acceptable to you?
Yes/No? y
Warning: The resulting partition is not properly aligned for best performance: 34s % 2048s != 0s
Ignore/Cancel?


This means that it needs to be multiples of 2048 sectors to be aligned
(this example is just an example with a disk image).

Brian

-- 
Brian C. Lane (PST8PDT) - weldr.io - lorax - parted - pykickstart

Message #13 received at 41577 <at> debbugs.gnu.org (full text, mbox):

From: Harald Dunkel <harald.dunkel <at> aixigo.com>
To: 41577 <at> debbugs.gnu.org
Subject: Re: bug#41577: closed (Re: bug#41577: automatic alignment)
Date: Fri, 29 May 2020 08:08:50 +0200

Much better, but IMHO there is still room for improvement. It could say
(for example)

(parted) mkpart primary 100000s 199999s
Warning: The resulting partition is not properly aligned for best performance.
Suggested is sectors 100352 .. 198655
Accept/Reject?


Just a suggestion, of course.

Regards
Harri

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