From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lana.hrz.tu-chemnitz.de ([134.109.132.3]) by canuck.infradead.org with esmtps (Exim 4.63 #1 (Red Hat Linux)) id 1I1fMq-0008V2-DQ for linux-mtd@lists.infradead.org; Fri, 22 Jun 2007 05:23:57 -0400 Message-ID: <467B952E.30308@informatik.tu-chemnitz.de> Date: Fri, 22 Jun 2007 11:23:58 +0200 From: =?ISO-8859-15?Q?Martin_D=E4umler?= MIME-Version: 1.0 To: dedekind@infradead.org Subject: Re: Real-time flash simulator References: <467B77F7.2000007@informatik.tu-chemnitz.de> <1182499773.4403.76.camel@sauron> In-Reply-To: <1182499773.4403.76.camel@sauron> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mtd@lists.infradead.org, =?ISO-8859-15?Q?Martin_D=E4umler?= List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hello Artem, On Fri, 2007-06-22 at 10:09 +0200, Artem Bityutskiy wrote: > I am not an expert in real-time, so I would ask you to elaborate on what > particularly makes nandsim not real-time? What are your requirements? The flash simulator has to simulate a raw flash memory with given timings, size, etc. Nandsim performs the delays by busy waiting. The question is if nandsim will meet this timings on every condition, e.g. under heavy load. This includes write operations as well as read operations. The simulator is just software but it has to be deterministic like real raw flash. This simulator should be a tool to examine the real time behaviour of flash file systems. >> Furthermore, there are some efforts to develop a (scaleable) real-time >> capable flash file system? > > We develop UBIFS (see MTD web site) but we do not set real-time > requirements. You are welcome to collaborate. The overall goal of my work is to develop respectively to examine the feasibility of a scaleable flash file system on raw flash. Like mentioned on the MTD web site this might be very difficult because of wear-levelling and bad block management. In my opinion, for real-time issues it is necessary to avoid garbage collection. So, a layer between file system and raw flash, performing wear-levelling and bad block management could be one approach to be investigated furhter. The real-time flash simulator is just one step in this direction. Regards, Martin