From owner-freebsd-fs@freebsd.org Sat Aug 8 10:06:41 2015 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 712E09B57B7 for ; Sat, 8 Aug 2015 10:06:41 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from mailman.ysv.freebsd.org (mailman.ysv.freebsd.org [IPv6:2001:1900:2254:206a::50:5]) by mx1.freebsd.org (Postfix) with ESMTP id 5A1E23B1 for ; Sat, 8 Aug 2015 10:06:41 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: by mailman.ysv.freebsd.org (Postfix) id 573239B57B6; Sat, 8 Aug 2015 10:06:41 +0000 (UTC) Delivered-To: fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 56CD59B57B5 for ; Sat, 8 Aug 2015 10:06:41 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from smtp.digiware.nl (smtp.digiware.nl [31.223.170.169]) (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 1BCD33B0 for ; Sat, 8 Aug 2015 10:06:40 +0000 (UTC) (envelope-from wjw@digiware.nl) Received: from rack1.digiware.nl (unknown [127.0.0.1]) by smtp.digiware.nl (Postfix) with ESMTP id 3D7BC1534C6 for ; Sat, 8 Aug 2015 12:06:32 +0200 (CEST) X-Virus-Scanned: amavisd-new at digiware.nl Received: from smtp.digiware.nl ([127.0.0.1]) by rack1.digiware.nl (rack1.digiware.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id QQyUEkQMZaBB; Sat, 8 Aug 2015 12:06:06 +0200 (CEST) Received: from [192.168.10.10] (asus [192.168.10.10]) by smtp.digiware.nl (Postfix) with ESMTPA id D55981534C7 for ; Sat, 8 Aug 2015 12:06:06 +0200 (CEST) To: fs@freebsd.org From: Willem Jan Withagen Subject: Using SSDs as swap Message-ID: <55C5D48E.6010605@digiware.nl> Date: Sat, 8 Aug 2015 12:06:06 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 08 Aug 2015 10:06:41 -0000 one of the following commits just passed with this in the log, and it triggered again a question I've been having for some time again already. ---- Log: Enable BIO_DELETE passthru in GELI, so TRIM/UNMAP can work as expected when GELI is used on a SSD or inside virtual machine, so that guest can tell host that it is no longer using some of the storage. ----- In ZFS I slice my SSD's into log and caches, but on a a server with little memory (which can't be grown) I use a partion on each ssd as swap as well. So swappinging does not have to seek, and has faster loading time. To allocate a few GB on aan SSD to swap is not really all that painfull, given current sizes, but the speed difference with regular spindels is impressive. But the questions are: 1) Does the swap driver understand that backing-store needs a TRIM? 1a) if not would it be useful, and what would it take to implement? 2) Does the SSD "suffer" unneeded from swapping on it? Thanx, --WjW