From owner-freebsd-fs@FreeBSD.ORG Sat Sep 18 00:55:35 2010 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 3F257106564A for ; Sat, 18 Sep 2010 00:55:35 +0000 (UTC) (envelope-from jhellenthal@gmail.com) Received: from mail-yw0-f54.google.com (mail-yw0-f54.google.com [209.85.213.54]) by mx1.freebsd.org (Postfix) with ESMTP id E046C8FC08 for ; Sat, 18 Sep 2010 00:55:34 +0000 (UTC) Received: by ywt2 with SMTP id 2so1123066ywt.13 for ; Fri, 17 Sep 2010 17:55:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:sender:message-id:date:from :user-agent:mime-version:to:cc:subject:references:in-reply-to :x-enigmail-version:content-type:content-transfer-encoding; bh=VTjJIthja9mK9Wy6GW7jxa/UJX4Q/mynH643QybPFwE=; b=Aw8NLKdM8sg+SD220sKWCUJQ3YfjityRKCRAk5F+L+q31JjdgaeKBZG8onu7t8Pf7Z 5TwCyIpmGUPfI7V0LXvAhYpCaQiSlfedvJ+EpCae1NKrjbBQ8LhHgQslGdzcrltYr7Sg IOJwHfWh/Po547Z/gupcb2xJ0cqaA4+7zFldY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:x-enigmail-version:content-type :content-transfer-encoding; b=k2ciQYp39o5gIXbyDa/FVSyZDSgokLWKwJqvvkopJaoZ/7KezXQhTBcz0mHMEBAVEC oSNikKm4odCdpilM5jUle9ejJW/8jHO5j5NZYCeuIw9nLLBMx/14z0I0+IX+tOm99Mop qua7KaoVYwHPJMGqTmrhCpuPDmQKiuueyDPbc= Received: by 10.150.47.37 with SMTP id u37mr6697324ybu.47.1284771333937; Fri, 17 Sep 2010 17:55:33 -0700 (PDT) Received: from centel.dataix.local (adsl-99-181-146-122.dsl.klmzmi.sbcglobal.net [99.181.146.122]) by mx.google.com with ESMTPS id w3sm261477ybi.7.2010.09.17.17.55.32 (version=SSLv3 cipher=RC4-MD5); Fri, 17 Sep 2010 17:55:33 -0700 (PDT) Sender: "J. Hellenthal" Message-ID: <4C940E02.1010405@DataIX.net> Date: Fri, 17 Sep 2010 20:55:30 -0400 From: jhell User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.9.2.9) Gecko/20100917 Lightning/1.0b1 Thunderbird MIME-Version: 1.0 To: Freddie Cash References: <4C9385B0.2080909@shatow.net> <20100917161847.GA58503@icarus.home.lan> In-Reply-To: X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org Subject: Re: what happens to pool if ZIL dies on ZFS v14 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: Sat, 18 Sep 2010 00:55:35 -0000 On 09/17/2010 13:09, Freddie Cash wrote: > On Fri, Sep 17, 2010 at 9:47 AM, Gil Vidals wrote: >> First, let me say that I'm receiving excellent input from the FreeBSD >> community. I'm new to FreeBSD and ZFS and this mailing list has been very >> helpful. >> >> I'm running ZFSv14 on FreeBSD 8.1 AMD64 with 8GB of DDR3 RAM with two SSDs - >> one for the ZIL and the other for the L2ARC cache. >> >> zambia# zpool iostat -v 1 1 >> capacity operations bandwidth >> pool used avail read write read write >> ---------------- ----- ----- ----- ----- ----- ----- >> tank 6.57G 921G 0 11 116K 438K >> mirror 6.57G 921G 0 5 116K 229K >> label/disk1 - - 0 3 57.9K 229K >> label/disk2 - - 0 3 57.8K 229K >> label/zilcache 136K 59.5G 0 6 17 209K >> cache - - - - - - >> label/l2cache 59.6G 8.50K 0 0 31.5K 48.9K >> ---------------- ----- ----- ----- ----- ----- ----- >> >> Observing the ZIL Cache, I see it being used very sparingly. And now that I >> know the SSD slog must be mirrored in ZFS < v19, I think the best course of >> action (assuming I'm not buying more equipment) is to mirror the ZIL SSD and >> abandon the L2ARC altogether. Won't RAM be used for L2ARC instead? > > The ZIL is only used for synchronous writes, and does not need to be > very large. I forget the formula for determining the exact size of a > ZIL (something along the lines of the max amount of data you can write > in 30 seconds), but it's rarely more than 4 GB and usually in the 1-2 > GB range. > > If possible, you'd be better off rebuilding your pool like so: > mirror disk1 and disk2 > slice both SSDs into two: 4-8 GB for ZIL, rest for L2ARC > mirror zilcache1 zilcache2 > add l2cache1 l2cache2 (don't mirror them) > > That way, you have a mirrored ZIL, and double the L2ARC. However, > since it takes around 270 bytes of RAM for every object in the L2ARC, > you'll want to make sure you have lots of RAM to manage it (or, > possibly, make 3 slices on the SSDs and use the third for swap?). > http://www.solarisinternals.com/wiki/index.php/ZFS_Evil_Tuning_Guide#Disabling_the_ZIL_.28Don.27t.29 -- jhell,v