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Re: Disk for a small server

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On 8/10/21 12:56 PM, Dan Ritter wrote:
> David Christensen wrote:
>> On 8/10/21 8:04 AM, Leandro Noferini wrote:
>>
>> https://wiki.debian.org/ZFS
>>
>>
>> But:
>>
>> - ZFS wants lots of memory.  The rule of thumb is 5 GB of memory for every 1
>> TB of storage.
> 
> This is a myth.


Oracle says [1]:

     "... for good ZFS performance, use at least one GB or more of memory."


The FreeBSD "ZFS Tuning Guide" says [2]:

     "To use ZFS, at least 1 GB of memory is recommended (for all
architectures) but more is helpful as ZFS needs *lots* of memory."

     "There are some resources that suggest that one needs 2GB per TB of
storage with deduplication ... . In practice with FreeBSD, based on
empirical testing and additional reading, it's closer to 5GB per TB."


(I use deduplication, so I recalled the "5 GB per TB".)


STFW there are other recommendations.


Looking ahead, I agree that deduplication does not make sense for the 
OP's use-case.  So, 1 GB of memory is supposed to be enough.  Benchmarks 
would be informative, but STFW I am unable to find such.


>> - ECC memory is safer than non-ECC memory.
> 
> This is true, but there is nothing that makes ZFS more dangerous
> than another filesystem using non-ECC memory.


I think the amount of danger depends upon how you do your risk 
assessment math.  I find used entry-level server hardware with ECC 
memory to be desirable for additional reasons.


>> - "dedup" is heavyweight, slow on HDD's (due to seek latency), and not
>> recommended for general workloads.
> 
> Not stated strongly enough. Nobody should turn on dedup; people
> who think they are experimenting should definitely not turn on
> dedup; only people who have a completely sacrificial system and
> a good knowledge of the data to be stored should consider dedup.


This article has some good information:

https://www.truenas.com/docs/references/zfsdeduplication/


I have been running deduplication for several years on my SOHO servers, 
which have HDD's and SATA3 SSD caches.  Normal read/ write operations 
can fill the Gigabit network, but replication is very slow (5.8 MB/s for 
a recent replication job).


David


[1] https://docs.oracle.com/cd/E18752_01/html/819-5461/gbgxg.html

[2] https://wiki.freebsd.org/ZFSTuningGuide

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Thread

Disk for a small server Leandro Noferini <lnoferin@cybervalley.org> - 2021-08-10 17:20 +0200
  Re: Disk for a small server ghe2001 <ghe2001@protonmail.com> - 2021-08-10 19:10 +0200
    Re: Disk for a small server Leandro Noferini <leandro@cybervalley.org> - 2021-08-10 20:30 +0200
      Re: Disk for a small server ghe2001 <ghe2001@protonmail.com> - 2021-08-10 20:50 +0200
      Re: Disk for a small server rhkramer@gmail.com - 2021-08-10 21:10 +0200
        Re: Disk for a small server Leandro Noferini <lnoferin@cybervalley.org> - 2021-08-10 21:10 +0200
          Re: Disk for a small server Thomas Amm <debili@open-email.net> - 2021-08-10 22:40 +0200
      Re: Disk for a small server Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-08-11 01:00 +0200
        Re: Disk for a small server Leandro Noferini <leandro@cybervalley.org> - 2021-08-11 11:20 +0200
          Re: Disk for a small server Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-08-11 12:30 +0200
  Re: Disk for a small server David Christensen <dpchrist@holgerdanske.com> - 2021-08-10 21:50 +0200
    Re: Disk for a small server Dan Ritter <dsr@randomstring.org> - 2021-08-10 22:00 +0200
      Re: Disk for a small server David Christensen <dpchrist@holgerdanske.com> - 2021-08-11 02:40 +0200
        Re: Disk for a small server Celejar <celejar@gmail.com> - 2021-08-11 05:00 +0200
          Re: Disk for a small server David Christensen <dpchrist@holgerdanske.com> - 2021-08-11 12:00 +0200
            Re: Memory and other hardware safety issue regarding ZFS [was Disk  for a small server] Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-08-11 12:30 +0200
            Re: Disk for a small server Celejar <celejar@gmail.com> - 2021-08-11 16:10 +0200
              Re: Disk for a small server David Christensen <dpchrist@holgerdanske.com> - 2021-08-11 23:50 +0200
                Re: Disk for a small server Stefan Monnier <monnier@iro.umontreal.ca> - 2021-08-12 00:00 +0200
                Re: Disk for a small server <tomas@tuxteam.de> - 2021-08-12 08:50 +0200
    Re: Disk for a small server <tomas@tuxteam.de> - 2021-08-10 22:00 +0200
      Re: Disk for a small server David Christensen <dpchrist@holgerdanske.com> - 2021-08-11 03:00 +0200

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