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Date:      Thu, 23 Apr 2020 18:57:24 -0400
From:      Chris Gordon <freebsd@theory14.net>
To:        David Christensen <dpchrist@holgerdanske.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: best upgrade process for server
Message-ID:  <22A86243-7351-4A2F-8B43-10E80C61901E@theory14.net>
In-Reply-To: <618aed37-a64b-9471-4353-366460d057d7@holgerdanske.com>
References:  <1810714722.149383351.1587616694832.JavaMail.zimbra@shaw.ca> <618aed37-a64b-9471-4353-366460d057d7@holgerdanske.com>

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> On Apr 23, 2020, at 4:25 PM, David Christensen =
<dpchrist@holgerdanske.com> wrote:
>=20
> When it was time to retire my previous desktop/ Linux SOHO server with =
an up-to-date FreeBSD server, I bought a lightly used Dell PowerEdge T30 =
with one Xeon E3-1225 v5 processor, one 8 GB ECC memory module, one 1 TB =
SATA HDD, and one DVD+/-RW drive.  (It is important that computers =
running ZFS have ECC memory.)

I would clarify the statement about ECC memory in that ECC memory is =
important for any system where memory errors are significantly =
detrimental to the applications running on the server whereas to justify =
the additional cost. =20

As for file systems, ECC memory is no more or less important for ZFS, =
UFS, ext*, NTFS, etc.  The only case where I think the argument for ZFS =
could be stronger than other file systems is by virtue of ZFS typically =
using more memory for the ARC and thereby theoretically increasing the =
probability of a read serviced from ARC experiencing a bit flip. This =
thinking, though, applies to applications, too --  as more memory is =
used, the probability of encountering a memory error increases.  The =
idea that ZFS uniquely "requires" ECC memory to be "safe" often seems to =
stem back to an a blog post about the "scrub of death".  This has been =
debunked many times.  Allan Jude discusses this is far more detail and =
expertise than I can starting at about minute 57 of Episode 200 of the =
BSDNOw podcast:  =
https://www.jupiterbroadcasting.com/116226/getting-scrubbed-to-death-bsd-n=
ow-200/

That said, if you can afford ECC memory, you're better than without it.  =
You are even better with backups that are on something other than the =
machine you're backing up.  You're even better if you can periodically =
test those backups and validate that they are indeed good and =
recoverable.

Chris=



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