From owner-freebsd-questions@FreeBSD.ORG Sat Jul 28 18:40:21 2012 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id CFDFD1065670 for ; Sat, 28 Jul 2012 18:40:21 +0000 (UTC) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Received: from wojtek.tensor.gdynia.pl (wojtek.tensor.gdynia.pl [89.206.35.99]) by mx1.freebsd.org (Postfix) with ESMTP id 21ED58FC08 for ; Sat, 28 Jul 2012 18:40:19 +0000 (UTC) Received: from wojtek.tensor.gdynia.pl (localhost [127.0.0.1]) by wojtek.tensor.gdynia.pl (8.14.5/8.14.5) with ESMTP id q6SIeHVR009978; Sat, 28 Jul 2012 20:40:18 +0200 (CEST) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Received: from localhost (wojtek@localhost) by wojtek.tensor.gdynia.pl (8.14.5/8.14.5/Submit) with ESMTP id q6SIMBf4009918; Sat, 28 Jul 2012 20:22:11 +0200 (CEST) (envelope-from wojtek@wojtek.tensor.gdynia.pl) Date: Sat, 28 Jul 2012 20:22:11 +0200 (CEST) From: Wojciech Puchar To: Vladimir Videscu In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.2.7 (wojtek.tensor.gdynia.pl [127.0.0.1]); Sat, 28 Jul 2012 20:40:18 +0200 (CEST) Cc: questions@freebsd.org Subject: Re: FreeBSD on SSD X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 28 Jul 2012 18:40:22 -0000 > The read-cache idea is very sound, mainly because by using it this way Seagate would not have to create a special set of > instructions for installing and using the HDD. I don't think that this drive cache is smart enough to really cache needed things and not flush that cache with useless data too often. i personally would prefer that drive to show up as 8GB disk and 750 GB disk. It would be easy to fit most of /usr in 8GB with even large set of software installed. when out of space then use softlinks and move not very used things (eg. documentation, non-yours locales, examples, some linarly accessed big files etc.) to disk. > My final question would be : > > Seeing as the HDD only has a SATA connector, this would mean that the SSD part already has a memory control device that regulates > access to that sector, whether it is a plain read-cache or not. This would imply that FreeBSD could communicate with the HDD > normally, through the SATA connector, just like any regular HDD. indeed. Such a drive is a good idea, but complete lack of documentation (how it operate) is not. You have to guess how this SSD-cache works because it is not documented. the other thing is erasing data. You want to sell that drive and clear your data by dd if=/dev/zero of=/dev/disk bs=1m but does it clear SSD cache? i don't think so. Someone sophisticated enough would perform raw read of cache chips and get cached data, which can actually be the most important part (things you work on often).