Re: OT: minimum bs for dd?

From	Andrei POPESCU <andreimpopescu@gmail.com>
Newsgroups	linux.debian.user
Subject	Re: OT: minimum bs for dd?
Date	2021-05-17 14:30 +0200
Message-ID	<CfKxI-6ML-7@gated-at.bofh.it> (permalink)
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On Lu, 17 mai 21, 10:00:22, tomas@tuxteam.de wrote:
> On Mon, May 17, 2021 at 10:29:06AM +0300, Andrei POPESCU wrote:
> > 
> > Hmm, would you (or anyone else) know what is the difference between 
> > oflags=sync and conv=fsync?
> 
> Let me put the docs next to each other (this is from the info page,
> which sometimes is more complete than the man page):

[snip informative quote from info page]

Ugh, forgot about the info/man distinction fro GNU software.

> I'd say "conv=fsync" does a sync at the end of the whole thing, while
> "oflag=sync" open(2)s the file with O_SYNC (likewise "oflag=dsync"
> translates to an open(2) with O_DSYNC), so the sync happens after each
> block write. That's what I want, since it gives me much more predictability
> as to when I can plop out my usb stick :)

If my understanding from your quotes and David's links is correct 
oflag=sync may be slower in specific circumstances, but it depends on so 
many factors (hardware, caches, block size used, etc.) that it is hard 
to predict.

Quite likely it won't make a significant difference for "regular" use.

Kind regards,
Andrei
-- 
http://wiki.debian.org/FAQsFromDebianUser

Thread

OT: minimum bs for dd? Bob Bernstein <poobah@ruptured-duck.com> - 2021-05-15 22:30 +0200
  Re: OT: minimum bs for dd? The Wanderer <wanderer@fastmail.fm> - 2021-05-15 22:40 +0200
  Re: OT: minimum bs for dd? IL Ka <kazakevichilya@gmail.com> - 2021-05-15 22:40 +0200
    Re: OT: minimum bs for dd? Bob Bernstein <bob@fanatick.org> - 2021-05-16 09:40 +0200
    Re: OT: minimum bs for dd? Michael Stone <mstone@debian.org> - 2021-05-16 19:50 +0200
      Re: OT: minimum bs for dd? Richard Owlett <rowlett@cloud85.net> - 2021-05-16 20:40 +0200
        Re: OT: minimum bs for dd? Stefan Monnier <monnier@iro.umontreal.ca> - 2021-05-17 00:40 +0200
          Re: OT: minimum bs for dd? The Wanderer <wanderer@fastmail.fm> - 2021-05-17 00:50 +0200
            Re: OT: minimum bs for dd? "Thomas Schmitt" <scdbackup@gmx.net> - 2021-05-17 09:00 +0200
              Re: OT: minimum bs for dd? The Wanderer <wanderer@fastmail.fm> - 2021-05-17 12:30 +0200
            Re: OT: minimum bs for dd? Greg Wooledge <greg@wooledge.org> - 2021-05-17 13:20 +0200
          Re: OT: minimum bs for dd? Andrei POPESCU <andreimpopescu@gmail.com> - 2021-05-17 08:10 +0200
            Re: OT: minimum bs for dd? <tomas@tuxteam.de> - 2021-05-17 08:40 +0200
              Re: OT: minimum bs for dd? Andrei POPESCU <andreimpopescu@gmail.com> - 2021-05-17 09:30 +0200
                Re: OT: minimum bs for dd? David <bouncingcats@gmail.com> - 2021-05-17 10:00 +0200
                Re: OT: minimum bs for dd? Andrei POPESCU <andreimpopescu@gmail.com> - 2021-05-17 14:10 +0200
                Re: OT: minimum bs for dd? <tomas@tuxteam.de> - 2021-05-17 10:10 +0200
                Re: OT: minimum bs for dd? Andrei POPESCU <andreimpopescu@gmail.com> - 2021-05-17 14:30 +0200
                Re: OT: minimum bs for dd? <tomas@tuxteam.de> - 2021-05-17 15:00 +0200
                info pages WHERE? -- was [Re: OT: minimum bs for dd?] Richard Owlett <rowlett@cloud85.net> - 2021-05-17 15:00 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] <tomas@tuxteam.de> - 2021-05-17 15:10 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Richard Owlett <rowlett@cloud85.net> - 2021-05-17 15:20 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] IL Ka <kazakevichilya@gmail.com> - 2021-05-17 15:30 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Richard Owlett <rowlett@cloud85.net> - 2021-05-17 16:00 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Greg Wooledge <greg@wooledge.org> - 2021-05-17 15:40 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] "Thomas Schmitt" <scdbackup@gmx.net> - 2021-05-17 16:10 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Greg Wooledge <greg@wooledge.org> - 2021-05-17 17:10 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] "Thomas Schmitt" <scdbackup@gmx.net> - 2021-05-17 18:00 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Brian <ad44@cityscape.co.uk> - 2021-05-17 20:30 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Greg Wooledge <greg@wooledge.org> - 2021-05-17 20:50 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] Brian <ad44@cityscape.co.uk> - 2021-05-17 21:00 +0200
                Re: info pages WHERE? -- was [Re: OT: minimum bs for dd?] <tomas@tuxteam.de> - 2021-05-17 16:10 +0200
            Re: OT: minimum bs for dd? Brian <ad44@cityscape.co.uk> - 2021-05-17 16:20 +0200
          Re: OT: minimum bs for dd? <tomas@tuxteam.de> - 2021-05-17 08:40 +0200
            Re: OT: minimum bs for dd? Richard Hector <richard@walnut.gen.nz> - 2021-05-17 13:40 +0200
        Re: OT: minimum bs for dd? Michael Stone <mstone@debian.org> - 2021-05-16 20:50 +0200
          Re: OT: minimum bs for dd? "Andrew M.A. Cater" <amacater@einval.com> - 2021-05-16 23:40 +0200

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