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Date:      Fri, 3 Sep 2021 16:49:02 -0400
From:      Kurt Hackenberg <kh@panix.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: FreeBSD 12.2-RELEASE-p9 trim: open failed: /dev/ada0: Operation not permitted
Message-ID:  <4019d92e-c33d-6ba1-dc80-7e28ccc44802@panix.com>
In-Reply-To: <64099455-5526-beb5-8ead-6ce8a9d073e6@holgerdanske.com>
References:  <dda0a570-53bc-7676-9f38-67bcd7a6f8bb@holgerdanske.com> <47d0f250-a47c-bbe0-2875-4f42f4464fcc@chezmarcotte.ca> <64099455-5526-beb5-8ead-6ce8a9d073e6@holgerdanske.com>

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On 2021/09/03 16:30, David Christensen wrote:

>> It might be that a raw device could be trimmed, but perhaps there's 
>> some safety there to stop it from wiping a device that is backing a 
>> mounted filesystem.
...
> That is a good point -- the filesystem knows what blocks are in use, 
> what blocks are not in use, and when blocks are removed from use. 
> Somehow, trim(8) gets this information (from the kernel filesystem stack?).
> 
> 
> RTFM trim(8):

Do I understand correctly that you want to set a state, so that the 
filesystem, ongoing, erases a block when it frees the block?

According to that man page, the trim command does something different: 
it erases blocks immediately, unconditionally, regardless of whether 
they're in use.

The man page says:

"The trim utility erases specified region of the device."

"The whole device is erased by default..."

If you're using ZFS, perhaps you should look for a way to configure the 
ZFS filesystem to erase on free.



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