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Date:      Wed, 7 Jul 2021 11:04:46 +0100
From:      Pete French <petefrench@ingresso.co.uk>
To:        Pete Wright <pete@nomadlogic.org>, Alan Somers <asomers@freebsd.org>
Cc:        Stefan Esser <se@freebsd.org>, FreeBSD Stable Mailing List <freebsd-stable@freebsd.org>
Subject:   Re: ZFS + mysql appears to be killing my SSD's
Message-ID:  <c340928a-d5a8-3890-bef9-379180f022b1@ingresso.co.uk>
In-Reply-To: <2e6dbe13-e08f-1dab-1f5b-76a90c3a2ea7@nomadlogic.org>
References:  <89c37c3e-22e8-006e-5826-33bd7db7739e@ingresso.co.uk> <2fd9b7e4-dc75-fedc-28d7-b98191167e6b@freebsd.org> <9c71d627-55b8-2464-6cc9-489e4ce98049@ingresso.co.uk> <CAOtMX2gWnEEKHHaDf0GmfC1wKAUqHK3ptNUxm23UFBsD_KHwKg@mail.gmail.com> <2e6dbe13-e08f-1dab-1f5b-76a90c3a2ea7@nomadlogic.org>

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On 07/07/2021 00:01, Pete Wright wrote:

> i also wonder if this could be a TRIM related issue.  according to 
> zpoolprops(8) TRIM is not enabled by default on pools - but it also has 
> this note (see autotrim):
> 
> "Be aware that automatic trimming of recently freed data blocks
> can put significant stress on the underlying storage devices.
> This will vary depending of how well the specific device handles
> these commands.  For lower end devices it is often possible to
> achieve most of the benefits of automatic trimming by running an
> on-demand (manual) TRIM periodically using the zpool trim
> command."
> 
> 
> I wonder if adjusting the autotrim feature will address these issues - i 
> manually enable autotrim for my pools and have seen no bad effects under 
> quite of bit of bursty i/o.  if it is enabled i wonder if the ssd you 
> are using doesn't play nice with autotrim and should stay disabled?

I was thinking this too - the autotrim stuff came in with OpenZFS, but I 
had trim enabled previously (I believe we had our own implementation on 
FreeBSD ZFS, is that right?). But I am wondering if a schduled trim 
might be a better option. Though the question arises as to 'how often' 
in that case.

-pete.



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