From owner-freebsd-fs@FreeBSD.ORG Fri Oct 4 10:42:27 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id DC958AD9 for ; Fri, 4 Oct 2013 10:42:27 +0000 (UTC) (envelope-from joh.hendriks@gmail.com) Received: from mail-ea0-x236.google.com (mail-ea0-x236.google.com [IPv6:2a00:1450:4013:c01::236]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 74E1C24DC for ; Fri, 4 Oct 2013 10:42:27 +0000 (UTC) Received: by mail-ea0-f182.google.com with SMTP id o10so1692895eaj.41 for ; Fri, 04 Oct 2013 03:42:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :references:in-reply-to:content-type:content-transfer-encoding; bh=DKySxSiN3ldlD2yiFJeeXyF1RLGkY4ESIlIJPcdIY0w=; b=Jz0CeIdpaAp1zYyDeKgBiq3400sQvHYUD+QdXxwIl0ZJfkhhN+R9UuQ/6xB2g+VXND oegEBWasuM8jFcdq9T45QEayVCKGaipYWasSeefjczvgbFAZCPVbjx4ftReNyCqug3/u HGIX7B9TvBiHpMkOqKRV8L1ZDrWaUzUWCdPnnVYn3BL7TGkZXpynznheiL7T49XPUv3R afW/WaNSsLanv67amr0kNmVhKc58BAZfRipQIDCFXbPxBVGYTYWIeQJsB5wy6TPLoUNY O4saRPPwhnfPrkx6NPFbduq3vHHDrtvjMl5/t00Tro+w33s9fMrNrO16dNsjA0SWtCZG 5y6w== X-Received: by 10.14.48.14 with SMTP id u14mr1514245eeb.74.1380883345927; Fri, 04 Oct 2013 03:42:25 -0700 (PDT) Received: from [192.168.1.129] ([193.173.55.180]) by mx.google.com with ESMTPSA id i1sm26596111eeg.0.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 04 Oct 2013 03:42:25 -0700 (PDT) Message-ID: <524E9B95.9010307@gmail.com> Date: Fri, 04 Oct 2013 12:42:29 +0200 From: Johan Hendriks User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Beeblebrox Subject: Re: Questions re swap-on-zfs References: <1380880223590-5848720.post@n5.nabble.com> In-Reply-To: <1380880223590-5848720.post@n5.nabble.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Oct 2013 10:42:27 -0000 Beeblebrox wrote: > I have 2 swap devices on my system. #1-tank0/swap on ZFS, #2-/dev/ada0p1 on > SSD 1GB. I have some questions for swap-on-zfs: > > 1. I had read in the past that swap-on-zfs can cause instability if memory > gets used to full capacity. Is this still the case, or has that issue been > corrected? The reason I created swap-#2 is precisely for this purpose; a > small backup resource. > > 2. If the problem still persists, I would like to tweak the setup so that > swap-#2 is only used as last resort. I tried setting the priority (pri) in > fstab, but it does not seem to work - how can this be done? > /dev/ada0p1 none swap sw,pri=0 0 0 > tank0/swap none zfs sw,pri=9 0 0 > > 3. Is it necessary for the data on swap to go through the Intent Log? I have > a separate ZIL device for tank0 pool. What risk is there if I disable the > log for the swap dataset? Is this done by modifying the "primarycache" > parameter for dataset? > > 4. Any other ideas to speed-up swap performance on tank0/swap? > > Regards. > I have one machine that has swap on ZFS. This is the only machine that hangs completely when a swap starvation occurs. It happens regualy because it is an old machine with only 2GB of RAM. That machine is running a version of FreeBSD 9.1 stable from april i guess. It is not an heavy duty server just an offsite backup system, so I can live with it. All other machines tho heavier on RAM have no problems even when a swap starvation occurs. I will not use swap on ZFS anymore. regards Johan Hendriks