From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 010896B0044 for ; Fri, 18 Dec 2009 15:31:27 -0500 (EST) Date: Fri, 18 Dec 2009 21:31:11 +0100 From: Ingo Molnar Subject: Re: Swap on flash SSDs Message-ID: <20091218203111.GA1390@elte.hu> References: <4B2A8D83.30305@redhat.com> <20091218051210.GA417@elte.hu> <1261161677.27372.1629.camel@nimitz> <4B2BD55A.10404@sgi.com> <1261164487.27372.1735.camel@nimitz> <20091218193911.GA6153@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Linus Torvalds Cc: Dave Hansen , Mike Travis , Christoph Lameter , Rik van Riel , Andrea Arcangeli , linux-mm@kvack.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Izik Eidus , Hugh Dickins , Nick Piggin , Mel Gorman , Andi Kleen , Benjamin Herrenschmidt , KAMEZAWA Hiroyuki , Chris Wright , Andrew Morton , "Stephen C. Tweedie" List-ID: * Linus Torvalds wrote: > On Fri, 18 Dec 2009, Ingo Molnar wrote: > > > > And even when a cell does go bad and all the spares are gone, the failure > > mode is not catastrophic like with a hard disk, but that particular cell > > goes read-only and you can still recover the info and use the remaining > > cells. > > Maybe. The real issue is the flash firmware. You want to bet it hasn't been > tested very well against wear-related failures in real life? I certainly dont want to bet anything on technology that is just a few years old :-) I have an SSD, and i keep backups. ( Okay, i have to admit that i have a weakness for certain types of unproven technology, such as toy kernels that are just a hobby ;-) > Once the flash firmware gets confused due to some bug, the end result is > usually a totally dead device. > > So failure modes can easily be pretty damn catastrophic. Not that that is in > any way specific to flash (the failures I've seen on rotational disks have > been generally catastrophic too - people who malign flashes for some reason > don't seem to admit that rotational media tends to have all the same > problems and then some). There's also electronics failure that could occur. Plus physical damage. But at least data recovery does not need a clean room ;-) [ If the cells are still undamaged, if it wasnt a lightning strike, an earthquake or a two year old that damaged them then an identical model can be used for recovery. ] ( If the data matters. If it doesnt then nobody will care about anything but everyday usability, a lifetime of at least a few months, plus price, performance/latency and maybe shock resistence. ) Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org