Date: Thu, 14 Apr 2016 20:01:35 -0600 From: Warner Losh <imp@bsdimp.com> To: Alfred Perlstein <bright@mu.org> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Heads up Message-ID: <CANCZdfrAyHhd4PP8JN9D7f_NwMybJRp_M8i2s3Cb0mtifQwSzQ@mail.gmail.com> In-Reply-To: <57104251.5080102@mu.org> References: <CANCZdfpnYnVrvhNagYUT9RhAuC1AMCrxh=GCt8RKT0bqxuJybw@mail.gmail.com> <57104251.5080102@mu.org>
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On Thu, Apr 14, 2016 at 7:22 PM, Alfred Perlstein <bright@mu.org> wrote: > > > On 4/14/16 3:42 PM, 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. >> >> Yowch... > > With data at stake wouldn't a whitelist be better along with a tool for > testing it? > > Example, you have whitelist and blacklist, if the device isn't on either > list you output a kernel message and suggest they run a tool to "test" the > controller and report back the findings? The only way to test it is to enable it. Run it for a day or six. If your data goes away, the drive is a lying sack. There's no tool to detect this that I've seen. You run the NCQ trim, it works. You do it again, it works again. After a while, if you have a bad drive model, bad things happen that are drive model specific. Did I mention that the black list matches Linux's black list and that only a tiny number of drive models lie. I guess I didn't. I am thinking of adding a tunable to turn it off though for people that are paranoid. Warner
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