Date: Mon, 2 Jun 2014 11:15:42 -0600 From: "Justin T. Gibbs" <gibbs@scsiguy.com> To: Mark Felder <feld@FreeBSD.org> Cc: freebsd-fs@freebsd.org, FreeBSD Hackers <freebsd-hackers@freebsd.org>, Matthew Ahrens <mahrens@delphix.com>, owner-freebsd-fs@freebsd.org, Nathan Whitehorn <nwhitehorn@freebsd.org> Subject: Re: fdisk(8) vs gpart(8), and gnop Message-ID: <61DC020F-F061-4A6E-AAEA-F0AE4CAE92F9@scsiguy.com> In-Reply-To: <c8ff89dc1993a3c6eb3daed97b247b13@mail.feld.me> References: <20140601004242.GA97224@bewilderbeast.blackhelicopters.org> <CAOjFWZ5N9FGwgSz0_YFNQjavzdJDitRn52VKn4ipW1ddj6-weQ@mail.gmail.com> <BCA9F5D6-3925-4E7E-9082-128652508305@FreeBSD.org> <3D6974D83AE9495E890D9F3CA654FA94@multiplay.co.uk> <538B4CEF.2030801@freebsd.org> <1DB2D63312CE439A96B23EAADFA9436E@multiplay.co.uk> <538B4FD7.4090000@freebsd.org> <CAJjvXiFAX7N-30g0OZ6idqLnyJww5dsyhGfLj6nYwKs9Xp--1g@mail.gmail.com> <538C9207.9040806@freebsd.org> <c8ff89dc1993a3c6eb3daed97b247b13@mail.feld.me>
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On Jun 2, 2014, at 9:49 AM, Mark Felder <feld@FreeBSD.org> wrote: > On 2014-06-02 10:02, Nathan Whitehorn wrote: >> My bigger concern is this pool upgrade one -- what if someone puts in >> a 4K disk in the future? >=20 > This is a concern of mine, and I sort of wish we did 4k by default and = forced people to override if they want 512b or something else. Adding a 4k sectored device is fine. You just need to use it in a new = top-level vdev in the pool. If you are at the point where you can=92t get new or compatible = warrantee replacements for the drives that may fail in your existing = pool, you should be migrating your data to new devices anyway. Mixing = devices with different performance characteristics within a TLV can lead = to pessimal behavior. I don=92t think that ZFS should jump through = large hoops to try and make this work well. Instead, we should = encourage the use of similar devices within a TLV (guidance that the = installer has sufficient information to provide*) and the system should = be optimized assuming this is how it will be used. I certainly *do not* want FreeBSD to automatically inflate the ashift = used on my pools. Doing so is an attempt to guess why I chose the = devices I did at pool creation time and my strategy for retiring them in = the future. The current proposal guesses wrong for me and the products = I help build. I=92d bet it will be wrong more times than right. =97 Justin *) Using the tools already in FreeBSD it is quite easy to group devices = by transport type, capacity, logical block size, physical block size, = and, for at least SCSI transports, media rotational speed. We do this = in Spectra=92s ZFS appliance so users have to work really hard to mix = devices that they shouldn=92t.=
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