Date: Mon, 18 Apr 2022 12:11:27 -0600 From: Scott Long <scottl@samsco.org> To: Warner Losh <imp@bsdimp.com> Cc: freebsd-scsi <freebsd-scsi@freebsd.org> Subject: Re: WWN Message-ID: <A3CE747F-4BEF-4B58-8769-B089221875FA@samsco.org> In-Reply-To: <CANCZdfr7u0Emk=%2B6butKsjAgYcgJhvTZu3rv7X6N6Pozdx7tcA@mail.gmail.com> References: <CANCZdfr7u0Emk=%2B6butKsjAgYcgJhvTZu3rv7X6N6Pozdx7tcA@mail.gmail.com>
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It=E2=80=99s been inertia from the hardware standpoint. SATA was = notorious for having unusable WWNs, serial numbers, etc. It=E2=80=99s = also been complicated by the varying quality of SATL and SATA-pass-thru = implementations in controllers (i.e. LSI). The Spectra guys probably = have a lot of good experience to share here. Keep VM=E2=80=99s in mind though. Emulated environments don=E2=80=99t = always try very hard to generate unique IDs for storage. It might be = possible to heuristically figure out what kind of environment the system = is in and whether the IDs are dependable. Scott > On Apr 18, 2022, at 11:47 AM, Warner Losh <imp@bsdimp.com> wrote: >=20 > Is there a reason we don't rely primarily on WWN changing to detect a = disk change at a particular location? I know it's not universally = available, but anything made in the last 15 or 20 years should have one = if my research is correct... Or is this just a case of inertia? >=20 > I'm looking at making ahci a little more resilient to transient = outages, and thought it might be best to key primarily off this and = secondarily off other changed information when that's not available. If = I had a WWN, then I'd know the disk that was gone for 500ms is the same = one and I could resume its operations and still detect that someone = unplugged drive A and plugged in drive B. >=20 > Warner >=20
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