From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mirko Benz Subject: Re: NVRAM support Date: Wed, 15 Feb 2006 09:24:06 +0100 Message-ID: <43F2E526.9010409@web.de> References: <43EC5655.1060504@web.de> <20060210124204.GC28676@harddisk-recovery.com> <43ECB4A4.6010005@tmr.com> <20060213092204.GB3209@harddisk-recovery.nl> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20060213092204.GB3209@harddisk-recovery.nl> Sender: linux-raid-owner@vger.kernel.org To: Erik Mouw Cc: dean gaudet , Bill Davidsen , linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, My intention was not to use a NVRAM device for swap. Enterprise storage systems use NVRAM for better data protection/faster=20 recovery in case of a crash. Modern CPUs can do RAID calculation very fast. But Linux RAID is=20 vulnerable when a crash during a write operation occurs. E.g. Data and parity write requests are issued in parallel but only one= =20 finishes. This will lead to inconsistent data. It will be undetected and can not be=20 repaired. Right? How can journaling be implemented within linux-raid? I have seen a paper that tries this in cooperation with a file system: =84Journal-guided Resynchronization for Software RAID=93 www.cs.wisc.edu/adsl/Publications But I would rather see a solution within md so that other file systems=20 or LVM can be used on top of md. Regards, Mirko Erik Mouw schrieb: > On Fri, Feb 10, 2006 at 05:02:02PM -0800, dean gaudet wrote: > =20 >> On Fri, 10 Feb 2006, Bill Davidsen wrote: >> =20 >>> Erik Mouw wrote: >>> =20 >>>> You could use it for an external journal, or you could use it as a= swap >>>> device. >>>> =20 >>>> =20 >>> Let me concur, I used external journal on SSD a decade ago with jfs= (AIX). If >>> you do a lot of operations which generate journal entries, file cre= ate, >>> delete, etc, then it will double your performance in some cases. Ot= herwise it >>> really doesn't help much, use as a swap device might be more helpfu= l depending >>> on your config. >>> =20 >> it doesn't seem to make any sense at all to use a non-volatile exter= nal=20 >> memory for swap... swap has no purpose past a power outage. >> =20 > > No, but it is a very fast swap device. Much faster than a hard drive. > > > Erik > > =20 - To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html