From owner-freebsd-fs@FreeBSD.ORG Tue Jan 24 08:58:49 2012 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 C3DCC1065673 for ; Tue, 24 Jan 2012 08:58:49 +0000 (UTC) (envelope-from alexander@leidinger.net) Received: from mail.ebusiness-leidinger.de (mail.ebusiness-leidinger.de [217.11.53.44]) by mx1.freebsd.org (Postfix) with ESMTP id 544A08FC1A for ; Tue, 24 Jan 2012 08:58:49 +0000 (UTC) Received: from outgoing.leidinger.net (p5796C495.dip.t-dialin.net [87.150.196.149]) by mail.ebusiness-leidinger.de (Postfix) with ESMTPSA id 2E1C68440C3; Tue, 24 Jan 2012 09:58:34 +0100 (CET) Received: from webmail.leidinger.net (webmail.Leidinger.net [IPv6:fd73:10c7:2053:1::3:102]) by outgoing.leidinger.net (Postfix) with ESMTPS id 6B7711750; Tue, 24 Jan 2012 09:58:31 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=Leidinger.net; s=outgoing-alex; t=1327395511; bh=etePRf0EYfZkfnmQfiSMcDjMWigaJecnU8RVkusZab4=; h=Date:Message-ID:From:To:Cc:Subject:References:In-Reply-To: Content-Type:MIME-Version; b=Z0gdk0/5vTg3OHB3I3jqxQt6bY1KOL1HxKU333p5aOsk4NgiY9K9KfAVdhmMO7Eso onFghI1gkG2J2ePs6kESVpUz1aNmSCpWbWyM436nsOAb6In7qxJYhOIs2BfIG/mNQu tsVPwiH3ozVrTlphUOOJrDuLAoBGww6cjpLGLQcucZ7792tl3Gt74jGm4i/zDSKAKc FgpFNOpbk+GuVMXMlbyWXd2UYrQhgVVbSmL1r4MVT6DU9h7TmA+uuM6UQ9dFf1OOxM 6HzjBzTa3EOSQHWQ8NvGSxG0XCpsw3twhpL8CLcMutYT2XjBgkVmHs3htp8x/ODF5q AqHJ4JHsd4E+Q== Received: (from www@localhost) by webmail.leidinger.net (8.14.5/8.14.4/Submit) id q0O8wT1x057246; Tue, 24 Jan 2012 09:58:29 +0100 (CET) (envelope-from Alexander@Leidinger.net) X-Authentication-Warning: webmail.leidinger.net: www set sender to Alexander@Leidinger.net using -f Received: from 85.94.224.19 ([85.94.224.19]) by webmail.leidinger.net (Horde Framework) with HTTP; Tue, 24 Jan 2012 09:58:29 +0100 Date: Tue, 24 Jan 2012 09:58:29 +0100 Message-ID: <20120124095829.Horde.cxpNZ5jmRSRPHnK1Ecp9wtA@webmail.leidinger.net> From: Alexander Leidinger To: Willem Jan Withagen References: <4F193D90.9020703@digiware.nl> <20120121162906.0000518c@unknown> <4F1B0177.8080909@digiware.nl> <20120121230616.00006267@unknown> <4F1BC493.10304@brockmann-consult.de> <4F1C3597.4040009@digiware.nl> In-Reply-To: <4F1C3597.4040009@digiware.nl> User-Agent: Internet Messaging Program (IMP) H4 (5.0.18) Content-Type: text/plain; charset=ISO-8859-1; format=flowed; DelSp=Yes MIME-Version: 1.0 Content-Disposition: inline X-EBL-MailScanner-Information: Please contact the ISP for more information X-EBL-MailScanner-ID: 2E1C68440C3.A0DB0 X-EBL-MailScanner: Found to be clean X-EBL-MailScanner-SpamCheck: not spam, spamhaus-ZEN, SpamAssassin (not cached, score=-0.1, required 6, autolearn=disabled, DKIM_SIGNED 0.10, DKIM_VALID -0.10, DKIM_VALID_AU -0.10) X-EBL-MailScanner-From: alexander@leidinger.net X-EBL-MailScanner-Watermark: 1328000315.18527@SOqCj1Ip6D68H2qshv4Upw X-EBL-Spam-Status: No Cc: freebsd-fs@freebsd.org Subject: Re: Question about ZFS with log and cache on SSD with GPT 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: Tue, 24 Jan 2012 08:58:49 -0000 Quoting Willem Jan Withagen (from Sun, 22 Jan 2012 17:13:11 +0100): > On 22-1-2012 9:10, Peter Maloney wrote: >> Am 21.01.2012 23:06, schrieb Alexander Leidinger: >>>> Corsair reports: >>>>> Max Random 4k Write (using IOMeter 08): 50k IOPS (4k aligned) >>>>> So I guess that suggests 4k aligned is required. >>> Sounds like it is. >>> >> I'm not an SSD expert, but I read as much as I can, and found that many >> say that the sector size is not the only thing that matters on an SSD, >> but also the *erase boundary*. The size of the erase boundary varies, >> but 2MiB is a common factor (or 1MiB for 99% of them), so you can use >> that for all. >> >> The theory I read about is that when the SSD wants to write something, >> it must erase the whole erase block first. If it needs to erase a whole >> erase boundary space to write 512 bytes, that is just normal. But if you >> are misaligned, it often needs to erase 2 erase boundary spaces. >> >> Here is an example from our FreeBSD forum: >> http://forums.freebsd.org/showthread.php?t=19093 > > Thanx for this thread, there is a lot of usefull info there. > pithy thing is to blow 66Mb, but then again on 40 or 120 Gb SSDs it is > only marginal. (Guess it stems from the time that HDs where 5Mb :) ) > > I'm still not really shure that that is needed it the bios has nothing > to do with these disks, as in our case: SSDs are only used as caches > under ZFS. I think the erase boundary only matters for speed, if the FS in question really deletes blocks in disk, instead of just "not using it anymore". I was told a while ago that ZFS is not doing BIO_DELETE, specially not on cache devices. So I do not expect that you will see an improvement by taking the erease boundary into account (except your SSD has not a decent wear-leveling implementation). Bye, Alexander. -- http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137