From owner-freebsd-questions@freebsd.org Wed Oct 18 20:11:43 2017 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B9238E42D9D for ; Wed, 18 Oct 2017 20:11:43 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-wr0-x243.google.com (mail-wr0-x243.google.com [IPv6:2a00:1450:400c:c0c::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4E2A5683C8 for ; Wed, 18 Oct 2017 20:11:43 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: by mail-wr0-x243.google.com with SMTP id u5so6231726wrc.5 for ; Wed, 18 Oct 2017 13:11:43 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=0clceyo02j4UiD7ro1JJ6kjDNcNW4g0uLCUpXXWAfQg=; b=NDHmaIew4dtniLL5glT+MA+m7mBH1aYvE/oddK/w97/5W0y5Av8t2DiDie4aXE/+B3 n9oMvyWrH78FGFNbZtuEUOnsG6kZnfogPL8OKCn0nCaABDeXdgXRO9GiKxe+LF0HNxFJ 4BhCv+US6SScXFaZtzjbp1YCn/gXLSCuRmFon2PEuBLjgrz6tqNNWuLxwGzwOig2YTtB 4UQNaYsmuFgL5ykEXtzajWnydmjVWPv/w3z0UpZzQe2Ud81yCL3f4ZvkL7qvaDvJVgC4 EcJCrIjtSakbXsUnJFTbBID7V3Waoserh0KWvU7BgrQvvwG0qsb/u3Qb2WQHvIvv72r/ e8Pw== X-Gm-Message-State: AMCzsaVU9R9WmIm2eIWWTzEcCPIuf/v8OewM42aJVLGv1JQUY1aSGAB4 74tM6a/8sSOvaFxPws2jlfduFg== X-Google-Smtp-Source: ABhQp+SEmUwq+dJlX56rcZnPvddNzV/LwQeqGid6ZPwlA7egQZ+y4jmA4y1BWW9tz6GgSLVqKY+3jQ== X-Received: by 10.223.162.139 with SMTP id s11mr7333023wra.231.1508357501389; Wed, 18 Oct 2017 13:11:41 -0700 (PDT) Received: from gumby.homeunix.com ([81.17.24.158]) by smtp.gmail.com with ESMTPSA id n11sm11517454wrh.71.2017.10.18.13.11.38 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 18 Oct 2017 13:11:40 -0700 (PDT) Date: Wed, 18 Oct 2017 21:11:36 +0100 From: RW To: freebsd-questions@freebsd.org Subject: Re: Md based tmpfs with zfs root system. Message-ID: <20171018211136.2f143b1a@gumby.homeunix.com> In-Reply-To: <20171018164559.GA3267@anza.vindaloo.com> References: <20171018164559.GA3267@anza.vindaloo.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; amd64-portbld-freebsd11.1) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Oct 2017 20:11:43 -0000 On Wed, 18 Oct 2017 12:45:59 -0400 Christopher Sean Hilton wrote: > Good day, > > I've using a new system with root on zfs. I've traditionally used a > /dev/md* based tmpfs for /tmp. A little initial reading on the subject > shows an argument about this practice but I didn't find any threads > that provide a resolution. md devices and tmpfs are two different things. tmpfs is a bit like an md device, but it has its own built-in file-system, so it only uses memory for current files, whereas an md device stores all the sectors that have ever been written to, even if they hold deleted files. I don't follow ZFS much, but unless there is a specific reason not to use tmpfs with zfs it's preferred over md devices. If the issue is the use of swap with zfs, neither tmpfs nor swap-backed md devices actually require swap.