From owner-freebsd-fs@FreeBSD.ORG Mon Sep 19 19:07:02 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EB6531065676 for ; Mon, 19 Sep 2011 19:07:01 +0000 (UTC) (envelope-from jusher71@yahoo.com) Received: from nm28.bullet.mail.ne1.yahoo.com (nm28.bullet.mail.ne1.yahoo.com [98.138.90.91]) by mx1.freebsd.org (Postfix) with SMTP id 9A71D8FC15 for ; Mon, 19 Sep 2011 19:07:01 +0000 (UTC) Received: from [98.138.90.52] by nm28.bullet.mail.ne1.yahoo.com with NNFMP; 19 Sep 2011 19:07:00 -0000 Received: from [98.138.89.232] by tm5.bullet.mail.ne1.yahoo.com with NNFMP; 19 Sep 2011 19:07:00 -0000 Received: from [127.0.0.1] by omp1047.mail.ne1.yahoo.com with NNFMP; 19 Sep 2011 19:07:00 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 828430.98107.bm@omp1047.mail.ne1.yahoo.com Received: (qmail 54433 invoked by uid 60001); 19 Sep 2011 19:07:00 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1316459220; bh=6ndsGbrugWP+sTuTFBLU3EtcVIbxPxxgKxXEleZfL8M=; h=X-YMail-OSG:Received:X-Mailer:Message-ID:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=bgXwQWInMsATdcjrf6AyZ7sIuthkS9XZmEiN2zZwBJr3PQjFsSVdpAu4ObLmB/VzyafX4C6C3YYFwJDeKG7QDvGN93lYA4gMJdY+fU/8yfIyyoksXfqxBFxPH0jjMwEAOFIgWxIfN1l6nJO2G9ayWuICMekNYHyPt0JyWJQvEIk= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:Message-ID:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=P1vveZOopkLOjWoG6KENpLv3p8mgkY2OH8NyYQ01gQuAUcDMm7VvsIjtQHhp3mCdfn5rE31vO087yWwK7L9hk4gFw97gtpV8Mt9VGxBqpz8drINNnNBKEpwMwLyZ0OoOBJIJqnkXuRh0e6IUAGH16BhcTkLBCSfKVqJSgldVDNs=; X-YMail-OSG: P5ZO3aEVM1nxu5KQ2iXyW8AvL_b5ch.7DJ7CnRgw6_K07O_ S5Fnz8fP4.UvkJJskPgOWYetyc2ZT3rOIZiETtgjo0dlzCMxAyny._tvYoHp hQ1sF0yp2CcwdLtWMme.qvUA196vx8b7_LmK6LJG0HXXu57uxryIMEXPGuvf jqJZqnLF7VKoiOio5ETuMnzkW961m3N8Yetq.gXN3xICzEZQmunMklqdwPGu EICgf3FGIMrUiQ5kESK23TNcBzTQHTJBh2JXiTaBFbV0Necnr0s6aFgxjG95 LFV1z0fO1SYtzmXYw0EUDXlnar_BpYT91CPaM5Zf7CRkLQdKJJRilK3PsXAT Z1si2gvTr_tz3PzGRBHg90AORPEc9mL6e_o9ou_.XESkoCfJKOQ4pplpDWNT Ce_lh Received: from [77.247.181.164] by web121209.mail.ne1.yahoo.com via HTTP; Mon, 19 Sep 2011 12:07:00 PDT X-Mailer: YahooMailClassic/14.0.5 YahooMailWebService/0.8.114.317681 Message-ID: <1316459220.35419.YahooMailClassic@web121209.mail.ne1.yahoo.com> Date: Mon, 19 Sep 2011 12:07:00 -0700 (PDT) From: Jason Usher To: freebsd-fs@freebsd.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: ZFS obn FreeBSD hardware model for 48 or 96 sata3 paths... X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 19 Sep 2011 19:07:02 -0000 =0A=0A--- On Sat, 9/17/11, Bob Friesenhahn w= rote:=0A=0A> 150KB is a relatively small file size given that the=0A> defau= lt zfs blocksize is 128KB.=A0 With so many files you=0A> should definitely = max out RAM first before using SSDs as a=0A> l2arc.=A0 It is important to r= ecognize that the ARC cache=0A> is not populated until data has been read.= =A0 The cache=0A> does not help unless the data has been accessed several= =0A> times. You will want to make sure that all metada and=0A> directories = are cached in RAM.=A0 Depending on how the=0A> files are used/accessed you = might even want to intentionally=0A> disable caching of file data.=0A=0A=0A= How does one make sure that all metadata and directories are cached in RAM?= Just run a 'find' on the filesystem, or a 'du' during the least busy time= of day ? Or is there a more elegant, or more direct way to read all of th= at in ?=0A=0AFurther, if this (small files, lots of them) dataset benefits = a lot from having the metadata and dirs read in, how can I KEEP that data i= n the cache, but not cache the file data (as you suggest, above) ?=0A=0ACan= I explicitly cache metadata/dirs in RAM, and cache file data in L2ARC ?=0A= =0A=0A=0A> Are the writes expected to be synchronous writes, or are=0A> the= y asynchronous?=A0 Are the writes expected to be=0A> primarily sequential (= e.g. whole file), or is data=0A> accessed/updated in place?=0A=0A=0AIt's a = mix, I'm afraid.