From owner-freebsd-questions@FreeBSD.ORG Thu Sep 17 14:35:39 2009 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 93D82106566B for ; Thu, 17 Sep 2009 14:35:39 +0000 (UTC) (envelope-from amsibamsi@gmail.com) Received: from mail-fx0-f210.google.com (mail-fx0-f210.google.com [209.85.220.210]) by mx1.freebsd.org (Postfix) with ESMTP id 1CD198FC0C for ; Thu, 17 Sep 2009 14:35:38 +0000 (UTC) Received: by fxm6 with SMTP id 6so66963fxm.43 for ; Thu, 17 Sep 2009 07:35:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=aCmr3ZubiAG59QaUtbSMs+WoLIsEAIzGIHaOWfqWSlY=; b=n8ZXv7WUeXS9B+Y/vDMmEKqfDAMbXOH4qRNiQh3hZD73kpd7lbNx2uiBhJVjMx5kKC TIkQivMCRTQUwyQ265BiwlpxfsBvjQKykFZi9dJQVxD7XUborAXm96BJcXroz1Nag/hW RRZsEl7P0NzLg4p3/C9k191vvHThT/6QhAujg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=Zmmz+xRB0TbIdM7VAA4no1gcdpRo7WhVm3lmPBxd47E5E81vaodGXQPeWhgRSYOqKs bEwt2mn9sC7SAlmqYSEIwVaA9gnKsnUYuHCTedH81F+ptu3MTeZfPuADzl/asoVrwLJ+ lvMfGrNo5sLjhCPG/ZjHZGi/oCvYcjxSnCUL4= MIME-Version: 1.0 Received: by 10.223.60.134 with SMTP id p6mr55598fah.95.1253198138007; Thu, 17 Sep 2009 07:35:38 -0700 (PDT) In-Reply-To: <4AB22B09.4070507@ibctech.ca> References: <7E2DB08A-9E11-47D7-904D-9F3D8490868E@gmail.com> <4AB22B09.4070507@ibctech.ca> Date: Thu, 17 Sep 2009 16:35:37 +0200 Message-ID: <29722c130909170735w24886ac9j8c5faaed15d17bb9@mail.gmail.com> From: Anselm Strauss To: Steve Bertrand , freebsd-questions@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 Cc: Subject: Re: ZFS on small systems 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: Thu, 17 Sep 2009 14:35:39 -0000 Thanks for your advice, Steve. I looked a bit at the source code and in /usr/src/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c and I found this: /* set min cache to 1/32 of all memory, or 16MB, whichever is more */ arc_c_min = MAX(arc_c / 4, 64<<18); Could this mean that 16 MB are already enough to run ZFS? On Thu, Sep 17, 2009 at 2:26 PM, Steve Bertrand wrote: > Anselm Strauss wrote: >> Hi, >> >> I'm interested in using ZFS on one of my small systems with 256 MB of >> RAM and 4 GB flash disk. Since ZFS is now considered production ready on >> FreeBSD I would like to use it as root filesystem and profit mainly from >> the cool snapshot features for easy backups. >> >> I found multiple recommendations to run ZFS only on systems with enough >> resources. But is this only a requirement if you want good performance >> or also for ZFS to function properly at all? > > I've found that on the i386 arch, that at minimum you need 756M of > memory to do anything really useful. Now, I don't know if this has > changed or not, but I doubt that the box would be useful for anything > with only 256M. > > With that said, I can keep a box running at max disk r/w for hours on > end with 2GB, and 1536M allocated/reserved for ZFS. > > Perhaps however that there have been enhancements introduced that I > don't know about, that allow ZFS to operate in such a small memory > address space, but for some reason I doubt it. If I'm wrong, someone > will let us know ;) > > Steve >