From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263290AbTJQB7U (ORCPT ); Thu, 16 Oct 2003 21:59:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263292AbTJQB7U (ORCPT ); Thu, 16 Oct 2003 21:59:20 -0400 Received: from smtp.bitmover.com ([192.132.92.12]:42148 "EHLO smtp.bitmover.com") by vger.kernel.org with ESMTP id S263290AbTJQB7T (ORCPT ); Thu, 16 Oct 2003 21:59:19 -0400 Date: Thu, 16 Oct 2003 18:59:12 -0700 From: Larry McVoy To: jlnance@unity.ncsu.edu Cc: linux-kernel@vger.kernel.org Subject: Re: Transparent compression in the FS Message-ID: <20031017015912.GA28158@work.bitmover.com> Mail-Followup-To: Larry McVoy , jlnance@unity.ncsu.edu, linux-kernel@vger.kernel.org References: <1066163449.4286.4.camel@Borogove> <20031015133305.GF24799@bitwizard.nl> <3F8D6417.8050409@pobox.com> <20031016162926.GF1663@velociraptor.random> <20031016172930.GA5653@work.bitmover.com> <20031016174927.GB25836@speare5-1-14> <20031016230448.GA29279@pegasys.ws> <20031017013245.GA6053@ncsu.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031017013245.GA6053@ncsu.edu> User-Agent: Mutt/1.4i X-MailScanner-Information: Please contact the ISP for more information X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam (whitelisted), SpamAssassin (score=0.3, required 7, AWL) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16, 2003 at 09:32:45PM -0400, jlnance@unity.ncsu.edu wrote: > Lots of machines dont have ECC ram and seem to work reasonably well. That's because you have two choices in RAM today: ECC and straight memory, no parity. So you never know that there is a problem until /bin/ls starts core dumping. BK users catch memory errors all the time because BK checksums the data. Even with a very (!) weak checksum we see it (we have retained, perhaps stupidly, backwards compat with SCCS' 16 bit checksum - not CRC). One nice thing about the weak checksum is that we can tell if it is a memory from looking at the got/wanted values for the checksum, single bit errors are obvious. It happens so frequently that we have learned to recognize it and tell the customer within seconds of getting the mail. -- --- Larry McVoy lm at bitmover.com http://www.bitmover.com/lm