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Groups > comp.os.linux.advocacy > #351159

Re: Why does it take less than 3 seconds to make the second copy of the 4 gig file ?

From moroney@world.std.spaamtrap.com (Michael Moroney)
Newsgroups comp.os.linux.advocacy, sci.physics
Subject Re: Why does it take less than 3 seconds to make the second copy of the 4 gig file ?
Date 2016-04-21 17:00 +0000
Organization The World : www.TheWorld.com : Since 1989
Message-ID <nfb0vc$ept$1@pcls7.std.com> (permalink)
References (3 earlier) <nf8sta$c82$1@dont-email.me> <Jeff-Relf.Me@Apr.20{2.55P.Seattle.2016}> <20160421000457.1505a0eb@maxa-pc> <Jeff-Relf.Me@Apr.20{5.08P.Seattle.2016}> <nf9tjg$7mi$1@dont-email.me>

Cross-posted to 2 groups.

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Peter =?UTF-8?B?S8O2aGxtYW5u?= <peter-koehlmann@t-online.de> writes:

> wrote:

>> After a ReBoot, it takes 11 seconds to copy a 4 gig file
>> to/from my TeraByte Samsung 850 EVO; after that,
>> it takes _less_ than 3 seconds to copy it again.   Why ?

>Because it is buffered in your memory, you clueless dimbulb.
>And no, it does *not* take just 3 seconds. You will need 7 seconds for the 
>operation to finish, even though the OS might tell you earlier that its done 
>(because of buffering). You simply can't bypass the physical limitations, 
>and those are around 500 MB/sec. In other words: The operation will take 7 
>seconds, not 3, you idiot

The difference between "write back caching" and "write through caching".
On a write, a disklike device (actual hard drive, RAID controller, Flash)
with cache can tell the OS "success" upon a write as soon as it gets the
data into its cache, or it can wait until the data is all safely onto
non-volatile media before returning success to the OS.  The first is much
faster than the second, but the second is much safer, in case something
goes wrong (such as a power failure at the wrong time in a poorly designed
system).

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The Inevitable Death of the Windows PC Homer <usenet@slated.org> - 2016-04-20 11:06 +0100
  Re: I don't have to hold no fucking phone. Homer <usenet@slated.org> - 2016-04-20 11:57 +0100
    Re: I don't have to hold no fucking phone. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-20 13:49 +0200
      Re: I don't have to hold no fucking phone. DFS <nospam@dfs.com> - 2016-04-20 10:07 -0400
        Re: I don't have to hold no fucking phone. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-20 19:12 +0200
          Copying a 3.5 gig file, locally, SATA III is not a (limiting) factor. Jeff-Relf.Me <@.> - 2016-04-20 11:57 -0700
            Re: Copying a 3.5 gig file, locally, SATA III is not a (limiting) factor. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-20 23:42 +0200
              Copying a 3.5 gig file from/to the Samsung 850 EVO isn't SATA III limited. Jeff-Relf.Me <@.> - 2016-04-20 14:55 -0700
                Re: Copying a 3.5 gig file from/to the Samsung 850 EVO isn't SATA III limited. Melzzzzz <mel@zzzzz.com> - 2016-04-21 00:04 +0200
                Why does it take less than 3 seconds to make the second copy of the 4 gig file ? Jeff-Relf.Me <@.> - 2016-04-20 17:08 -0700
                Re: Why does it take less than 3 seconds to make the second copy of the 4 gig file ? Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-21 09:00 +0200
                Re: Why does it take less than 3 seconds to make the second copy of the 4 gig file ? moroney@world.std.spaamtrap.com (Michael Moroney) - 2016-04-21 17:00 +0000
                Re: Why does it take less than 3 seconds to make the second copy of the 4 gig file ? Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-21 19:05 +0200
            Re: Copying a 3.5 gig file, locally, SATA III is not a (limiting) factor. Incubus <incubus9536612@gmail.com> - 2016-04-22 06:07 -0700
          Re: I don't have to hold no fucking phone. DFS <nospam@dfs.com> - 2016-04-22 10:09 -0400
            The first copy ( of a 4 gig file ) takes 11 seconds. Jeff-Relf.Me <@.> - 2016-04-22 11:55 -0700
              Re: The first copy ( of a 4 gig file ) takes 11 seconds. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-22 23:27 +0200
                Re: The first copy ( of a 4 gig file ) takes 11 seconds. Richard King <kingsley651@webby.org> - 2016-04-22 17:55 -0400
                Re: The first copy ( of a 4 gig file ) takes 11 seconds. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-23 00:05 +0200
                Re: The first copy ( of a 4 gig file ) takes 11 seconds. Richard King <kingsley651@webby.org> - 2016-04-22 18:20 -0400
                Re: The first copy ( of a 4 gig file ) takes 11 seconds. Peter Köhlmann <peter-koehlmann@t-online.de> - 2016-04-23 01:01 +0200
                Re: The first copy ( of a 4 gig file ) takes 11 seconds. Richard King <kingsley651@webby.org> - 2016-04-22 19:11 -0400
    Re: I don't have to hold no fucking phone. chrisv <chrisv@nospam.invalid> - 2016-04-20 07:05 -0500
      Re: I don't have to hold no fucking phone. Sandman <mr@sandman.net> - 2016-04-20 12:28 +0000
    Re: The subjective preferences of the dying minority Homer <usenet@slated.org> - 2016-04-20 13:58 +0100
  Re: The Inevitable Death of the Windows PC DFS <nospam@dfs.com> - 2016-04-20 10:18 -0400
  Re: The Inevitable Death of the Windows PC ronb <ronb02NOSPAM@gmail.com> - 2016-04-20 17:09 +0000
    Re: The Inevitable Death of the Windows PC Me Sham <osirus47@yahoo.com> - 2016-04-20 10:38 -0700
      Re: The Inevitable Death of the Windows PC Desk Rabbit <me@example.com> - 2016-04-22 12:11 +0100
  Re: The Inevitable Death of the Windows PC 7 <7@enemygadgets.com> - 2016-04-20 20:51 +0000
  Re: The Inevitable Death of the Windows PC JEDIDIAH <jedi@nomad.mishnet> - 2016-04-20 15:53 -0500
    Re: The Inevitable Death of the Windows PC 7 <7@enemygadgets.com> - 2016-04-20 22:01 +0000
      Re: The Inevitable Death of the Windows PC Desk Rabbit <me@example.com> - 2016-04-22 12:14 +0100
        Re: The Inevitable Death of the Windows PC GreyCloud <mist@cumulus.com> - 2016-04-22 16:37 -0600

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