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Re: how to enable trim for an external encrypted SSD?

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On 07.11.2017 01:43, Michael Stone wrote:
> On Tue, Nov 07, 2017 at 01:00:54AM +0500, Alexander V. Makartsev wrote:
>> Now I wonder, why would anyone want to use TRIM feature on a portable
>> SSD,
>> especially on an encrypted one?
>> Isn't this feature only increases drive wear, offering next to
>> nothing as a
>> benefit in return?
>> I don't use TRIM feature on my systems because of that, and hope for
>> a firmware
>> of modern SSD will manage everything automatically. Am I wrong?
>
> TRIM should reduce, not increase, drive wear. (Since the drive knows
> that a particular block is unusued, it can write directly instead of
> having to read and rewrite an entire erase group.)
As I know SSDs are different in a way HDDs write their data. HDDs write
directly to the free block and are done. SSDs on the other hand will
have to erase free block first to get it ready for writing and then
write to it. This is because how NAND work. It's even worse, if a
destination block has some data on it already and there is some data
needs to be written onto it, then SSD will copy data already written,
then it will fully erase destination block, then it will concatenate
copied data with data to be written and finally will write merged data
to the block.
TRIM will erase blocks marked as deleted beforehand even if they are not
needed for writing right now. This overhead is the reason that causes
increased drive wear and decrease it's lifespan.

I do agree, that using fstune manually once in say half a year on a non
busy SSD could improve writing performance for some time, but using
discard or equivalent permanently in fstab is hardly worth it.

-- 
With kindest regards, Alexander.

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⢿⡄⠘⠷⠚⠋⠀ https://www.debian.org
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how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-06 13:10 +0100
  Re: how to enable trim for an external encrypted SSD? Christian Seiler <christian@iwakd.de> - 2017-11-06 14:30 +0100
    Re: how to enable trim for an external encrypted SSD? "Alexander V. Makartsev" <avbetev@gmail.com> - 2017-11-06 21:10 +0100
      Re: how to enable trim for an external encrypted SSD? Michael Stone <mstone@debian.org> - 2017-11-06 21:50 +0100
        Re: how to enable trim for an external encrypted SSD? "Alexander V. Makartsev" <avbetev@gmail.com> - 2017-11-06 22:30 +0100
          Re: how to enable trim for an external encrypted SSD? Michael Stone <mstone@debian.org> - 2017-11-06 23:10 +0100
            Re: how to enable trim for an external encrypted SSD? "Alexander V. Makartsev" <avbetev@gmail.com> - 2017-11-07 00:20 +0100
              Re: ow to enable trim for an external encrypted SSD? dekkzz78@gmail.com - 2017-11-07 13:40 +0100
          Re: how to enable trim for an external encrypted SSD? Henrique de Moraes Holschuh <hmh@debian.org> - 2017-11-07 02:10 +0100
      Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-07 08:20 +0100
    Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-07 08:10 +0100
    Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-11 14:10 +0100
      Re: how to enable trim for an external encrypted SSD? Christian Seiler <christian@iwakd.de> - 2017-11-11 14:20 +0100
        Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-11 14:40 +0100
          Re: how to enable trim for an external encrypted SSD? Christian Seiler <christian@iwakd.de> - 2017-11-11 15:30 +0100
            Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-11 16:50 +0100
              Re: how to enable trim for an external encrypted SSD? Stefan Monnier <monnier@iro.umontreal.ca> - 2017-11-16 04:10 +0100
                Re: how to enable trim for an external encrypted SSD? Joerg Desch <news@jdesch.de> - 2017-11-21 18:40 +0100
    Re: how to enable trim for an external encrypted SSD? Christian Seiler <christian@iwakd.de> - 2017-12-18 13:20 +0100

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