From owner-freebsd-questions@FreeBSD.ORG Sun Jun 15 01:08:32 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id CEDA21065674 for ; Sun, 15 Jun 2008 01:08:32 +0000 (UTC) (envelope-from kris@FreeBSD.org) Received: from weak.local (freefall.freebsd.org [IPv6:2001:4f8:fff6::28]) by mx1.freebsd.org (Postfix) with ESMTP id 049598FC13; Sun, 15 Jun 2008 01:08:31 +0000 (UTC) (envelope-from kris@FreeBSD.org) Message-ID: <48546B92.5050906@FreeBSD.org> Date: Sun, 15 Jun 2008 03:08:34 +0200 From: Kris Kennaway User-Agent: Thunderbird 2.0.0.14 (Macintosh/20080421) MIME-Version: 1.0 To: RW References: <20080614224742.17316919@gumby.homeunix.com.> <48545212.4040006@FreeBSD.org> <20080615013158.7dd19cf0@gumby.homeunix.com.> In-Reply-To: <20080615013158.7dd19cf0@gumby.homeunix.com.> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-questions@freebsd.org Subject: Re: md devices mounted with async X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 15 Jun 2008 01:08:32 -0000 RW wrote: > On Sun, 15 Jun 2008 01:19:46 +0200 > Kris Kennaway wrote: > >> RW wrote: >>> mdmfs(8) has an example of a malloc-backed md device mounted with >>> the async option. Is there any point in doing this with malloc and >>> vnode devices? In neither case does a write to the file-system >>> require a write to a physical disk. >> Well, for vnode devices it does write to the disk, > > I meant that a write to the filesystem doesn't require a corresponding > write to disk, and the change can stay in memory indefinitely. > Presumably, more or less, the same inactive pages get written-out to > swap, with or without async. Well, it doesn't necessarily cause a write to disk for each filesystem write, but the synchronization mode of the filesystem to the backing store is precisely what the async/noasync/sync mount options control! >> but that isn't the >> point; in both cases you are writing to the filesystem that is >> mounted on top of the md, so that will be faster if it is mounted >> async. > > In that case, why doesn't /etc/rc.d/tmp default to mounting its > swap-backed /tmp with async? It should. Kris