From owner-freebsd-current@FreeBSD.ORG Fri Nov 13 02:24:03 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3172E106566B; Fri, 13 Nov 2009 02:24:03 +0000 (UTC) (envelope-from artemb@gmail.com) Received: from mail-iw0-f190.google.com (mail-iw0-f190.google.com [209.85.223.190]) by mx1.freebsd.org (Postfix) with ESMTP id D4D418FC14; Fri, 13 Nov 2009 02:24:02 +0000 (UTC) Received: by iwn28 with SMTP id 28so2337938iwn.3 for ; Thu, 12 Nov 2009 18:24:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to:cc :content-type; bh=eTvmuwlQVyN+8bC6KtJHVxTVEN0E8qXWbpni1+A/S5k=; b=MXPzMfCFyD7CA1+dgDg5EW/Vx1XqDY4v7ApCn0pvx7dCEnZ1mTY3CKkvF0A5JZ/VWi qqbv0gtXIZEM5isGjwpqDjg4ZgGd/pBwnTsmRM5GHjLknSfOVkbopQASnxBzolbrWygN sxiMX/a24ssYp7rF2z8GKcolFFSTyU09+geD8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=gIF8yhogptZBQ9FRY5399kN8GeRpDmoBTQOpWuycxQJy5qWd6b6Iz9Gkw+qf/6J4wV NXFsgOD2nJ2sImWuVtcM+i5U43pkaRmFWyRu83y5x4szXXOCT0Wc/7wstD+//eYxFJbI ovXB5DC6K88U7OiAQJnk73s9hacl9lljvMosE= MIME-Version: 1.0 Sender: artemb@gmail.com Received: by 10.231.161.138 with SMTP id r10mr1684874ibx.34.1258079041900; Thu, 12 Nov 2009 18:24:01 -0800 (PST) In-Reply-To: <11167f520911121813v29441ac4v2e3dfa6f4386ba4e@mail.gmail.com> References: <11167f520911111050j36dd94far667c81e6f5c18e69@mail.gmail.com> <11167f520911121044l74744c30u5a4d9ca008ab863c@mail.gmail.com> <11167f520911121101o403751ddmb544dfaf1c61bf1e@mail.gmail.com> <11167f520911121339y4161a1a2sae8b6196c3b7a1fb@mail.gmail.com> <11167f520911121813v29441ac4v2e3dfa6f4386ba4e@mail.gmail.com> Date: Thu, 12 Nov 2009 18:24:01 -0800 X-Google-Sender-Auth: 7b9af4c0153abff3 Message-ID: From: Artem Belevich To: "Sam Fourman Jr." Content-Type: text/plain; charset=ISO-8859-1 Cc: Rick Macklem , Dan Nelson , Ivan Voras , freebsd-current@freebsd.org, Scott Ullrich Subject: Re: Help ZFS FreeBSD 8.0 RC2 Write performance issue X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 Nov 2009 02:24:03 -0000 On Thu, Nov 12, 2009 at 6:13 PM, Sam Fourman Jr. wrote: > so you are suggesting that it is possible that 2x SSD disks would get > me the other 60MB/sec I guess you can test what SSDs would buy you in terms of performance. Disable ZIL and run your performance test. If ZIL is what's causing issues, then you will see a speedup. In this case proper log on SSDs should bring your performance fairly close to those numbers, provided SSDs can handle your write rate. If disabling ZIL does not help much, then separate log device will not help much either. On a side note, log device does not have to be big. According to Sun you'll need ~1/2 of your physical memory size: http://docs.sun.com/app/docs/doc/819-5461/gfgaa?a=view Given that typical SSDs these days are quite a bit larger than your typical RAM size, you may use the rest of the SSD as L2ARC. --Artem