From owner-freebsd-questions@FreeBSD.ORG Thu Mar 26 12:46:50 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7F90D25A for ; Thu, 26 Mar 2015 12:46:50 +0000 (UTC) Received: from bede.qeng-ho.org (bede.qeng-ho.org [217.155.128.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 06ED4133 for ; Thu, 26 Mar 2015 12:46:49 +0000 (UTC) Received: from arthur.home.qeng-ho.org (arthur.home.qeng-ho.org [172.23.1.2]) by bede.home.qeng-ho.org (8.14.9/8.14.7) with ESMTP id t2QCkeix020612 for ; Thu, 26 Mar 2015 12:46:40 GMT (envelope-from freebsd@qeng-ho.org) Message-ID: <5513FFB0.8000100@qeng-ho.org> Date: Thu, 26 Mar 2015 12:46:40 +0000 From: Arthur Chance User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: FreeBSD-Questions Subject: Swap, SSDs and ZFS Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 Mar 2015 12:46:50 -0000 Warren Block's page on using SSDs with FreeBSD (http://www.wonkity.com/~wblock/docs/html/ssd.html) suggests that as swap doesn't use TRIM it's better to use a swap file if your disk is an SSD. However, this is in the context of a UFS file system. What if you have a pure ZFS system? Searching for an answer I found mailing list threads that say that ZVOLs can hang when under memory pressure, i.e. at the exact point when you need swap, so aren't recommended. However using a swap file will potentially waste space if the file system has snapshots. What do other people do in these circumstances? -- Those who do not learn from computing history are doomed to GOTO 1