Date: Wed, 15 May 2019 08:28:01 -0700 From: George Hartzell <hartzell@alerce.com> To: Matthias Oestreicher <matthias@smormegpa.no> Cc: hartzell@alerce.com, freebsd-questions@freebsd.org Subject: Re: Suggestions for working with unstable nvme dev names in AWS Message-ID: <23772.12290.9.225257@alice.local> In-Reply-To: <5917c50c94750782cb3a929d44b04bcce142ece2.camel@smormegpa.no> References: <23770.10599.687213.86492@alice.local> <08660a2a-489f-8172-22ee-47aeba315986@FreeBSD.org> <23770.58821.826610.399467@alice.local> <20190514210203.3d951fb8.freebsd@edvax.de> <23771.5612.105696.170743@alice.local> <eb1d290e48b4ba21ab350044b25592525e61457c.camel@smormegpa.no> <23771.11429.855191.658934@alice.local> <5917c50c94750782cb3a929d44b04bcce142ece2.camel@smormegpa.no>
next in thread | previous in thread | raw e-mail | index | archive | help
Matthias Oestreicher writes: > [...] > I have to admit that I'm still a bit unsure if I understand your problem. > > You are worried about, that the big-slow and the small-fast change their > device names when the system boots... > The GPT labels I suggested will survive a reboot, so no need to run a script > each time the system boots, to reapply those labels to the right drive. > > What you only need to do once, is to determine which /dev/nvmN is the big-slow > one and which the small-fast. Then you apply your labels, e.g.: > [...] Thanks again for following up. The final sentence in the bit I've quoted from your reply is the core of the problem. You/I request two additional block devices from Amazon, and we suggest the names that we'd like them to be given (e.g. `/dev/sdy` and `/dev/sdz`) but when the machine boots, it gives them the names `/dev/nvme1` and `/dev/nvme2` *and the names are assigned at random*. Sometimes `/dev/nvme1` is the device you asked to be named `/dev/sdy` and sometimes it's `/dev/sdz`. Perhaps it's more useful to say that I can never guess/know the device names, when the machine is powered up for the first time and when it is power cycled. As a human, how do I know which of the two devices is the big-slow one and which is the small-fast one. I suppose that I could run `dmesg` and look at their sizes? But what if they were the same size? What if they were identical except that they had different AWS snapshot policies? And/but, my goal is to be able to set up the machine automatically (this is "The Cloud(tm)", after all...). Because Amazon stashes the requested names somewhere in the volumes and provides a Linux tool that digs it out via an ioctl, one can figure it all out. I suspect that FreeBSD hasn't spent as much time on AWS and that the equivalent tool/ioctl isn't available. That's what I'm trying to check. Thanks again! g.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?23772.12290.9.225257>