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Subject: Re: Heads up
To: freebsd-current@freebsd.org
References: <CANCZdfpnYnVrvhNagYUT9RhAuC1AMCrxh=GCt8RKT0bqxuJybw@mail.gmail.com>
From: Graham Menhennitt <graham@menhennitt.com.au>
Message-ID: <57102067.6060708@menhennitt.com.au>
Date: Fri, 15 Apr 2016 08:57:43 +1000
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On 15/04/2016 8:42 AM, Warner Losh wrote:
> The CAM I/O scheduler has been committed to current. This work is described
> in https://people.freebsd.org/~imp/bsdcan2015/iosched-v3.pdf though the
> default scheduler doesn't change the default (old) behavior.
>
> One possible issue, however, is that it also enables NCQ Trims on ada SSDs.
> There are a few rogue drives that claim support for this feature, but
> actually implement data corrupt instead of queued trims. The list of known
> rogues is believed to be complete, but some caution is in order.
>
>
What sort of caution, please? How do we check whether it's working? Is 
it an "all or nothing" type of thing, or could there be subtle problems?

Thanks,
     Graham