From owner-freebsd-hackers Mon Mar 9 15:02:32 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA22617 for freebsd-hackers-outgoing; Mon, 9 Mar 1998 15:02:32 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from smtp02.primenet.com (smtp02.primenet.com [206.165.6.132]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA22400 for ; Mon, 9 Mar 1998 15:02:02 -0800 (PST) (envelope-from tlambert@usr08.primenet.com) Received: (from daemon@localhost) by smtp02.primenet.com (8.8.8/8.8.8) id QAA26608; Mon, 9 Mar 1998 16:01:34 -0700 (MST) Received: from usr08.primenet.com(206.165.6.208) via SMTP by smtp02.primenet.com, id smtpd026580; Mon Mar 9 16:01:33 1998 Received: (from tlambert@localhost) by usr08.primenet.com (8.8.5/8.8.5) id QAA04865; Mon, 9 Mar 1998 16:01:16 -0700 (MST) From: Terry Lambert Message-Id: <199803092301.QAA04865@usr08.primenet.com> Subject: Re: SCSI Bus redundancy... To: shimon@simon-shapiro.org Date: Mon, 9 Mar 1998 23:01:16 +0000 (GMT) Cc: lada@ws2301.gud.siemens.at, dmlb@ragnet.demon.co.uk, wilko@yedi.iaf.nl, julian@whistle.com, hackers@FreeBSD.ORG, lada@ws2301.gud.siemens.co.at In-Reply-To: from "Simon Shapiro" at Mar 9, 98 09:49:07 am X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > OLTP does not exists in Austria (i.e. not over Internet). The secure ******* > OLTP, at least what I mean by OLTP, is a concept/transaction type; On-Line > Transaction Processing. As Such it exists in Australia. Has nothing to do ********* 8-). I think he was thinking of OLTP in terms of E-Commerce services not existing in his country. > What I am trying to acomplish in this conversation, is that the range of > services and their sensitivity to interruption is wide. FreeBSD is > migrating from a hacker's desktop to a high caliber server. Some services > and features need to acompany this migration, or it will fail. > All O/Ss going into the service market are going through this perocess. M$ > Nice Try is already going there. This is a salient point. The ISP's who are interested in the HA aspects of such servers are more interested because of interruption of service issues, more than they are concerned with data-vaulting. I'm personally more concerned with being able to lock down the gears into a known-to-the-OS state, at all times. I can deal with rolling incomplete transactions back seperately, if I need transactions. The disk write cache is problematic. Most modern disks, when they lose DC, do *not* flush the dirty portion of their write cache. Because the cache is permitted to reorder operations without regard to their OS dependency order, this means that a write cache that's not written completely potentially damages dependency ordered data that the OS believes has been written. Dependency ordered data like that created by DOW or Soft Updates technologies. With disk write caching turned on, I still need a UPS to be able to do this reliably, since I have to (1) not add more work to the write cache which might potentially push out already delayed writes, and (2) cause the disk to flush it's write cache. High availability can also mean "comes back up quickly, and is robust in the face of deleterious conditions". Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message