From owner-freebsd-questions@FreeBSD.ORG Mon May 7 19:30:29 2007 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id B6D7816A406 for ; Mon, 7 May 2007 19:30:29 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from mail-out3.apple.com (mail-out3.apple.com [17.254.13.22]) by mx1.freebsd.org (Postfix) with ESMTP id 9D53413C457 for ; Mon, 7 May 2007 19:30:29 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from relay6.apple.com (relay6.apple.com [17.128.113.36]) by mail-out3.apple.com (Postfix) with ESMTP id 34BCDAAC8E; Mon, 7 May 2007 12:30:22 -0700 (PDT) Received: from relay6.apple.com (unknown [127.0.0.1]) by relay6.apple.com (Symantec Mail Security) with ESMTP id 53064100AB; Mon, 7 May 2007 12:30:29 -0700 (PDT) X-AuditID: 11807124-a52bfbb000001b27-53-463f7e55713f Received: from [17.214.13.96] (cswiger1.apple.com [17.214.13.96]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by relay6.apple.com (Apple SCV relay) with ESMTP id 3C55A10022; Mon, 7 May 2007 12:30:29 -0700 (PDT) In-Reply-To: <20070504171053.41eddb6a@gumby.homeunix.com> References: <20070503014137.I3544@duane.dbq.yournetplus.com> <20070503015723.S3544@duane.dbq.yournetplus.com> <4639FAB6.9050701@mac.com> <20070504171053.41eddb6a@gumby.homeunix.com> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <7967B2A8-3FF5-46AD-AFEA-9EE5C680A414@mac.com> Content-Transfer-Encoding: 7bit From: Chuck Swiger Date: Mon, 7 May 2007 12:30:29 -0700 To: RW X-Mailer: Apple Mail (2.752.2) X-Brightmail-Tracker: AAAAAA== Cc: freebsd-questions@freebsd.org Subject: Re: Time Synchronizing Between Two Servers X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 May 2007 19:30:29 -0000 On May 4, 2007, at 9:10 AM, RW wrote: > On Thu, 03 May 2007 11:07:34 -0400 > Chuck Swiger wrote: >> Sun SPARC machines have good HW clocks, and also some of the newer >> Macs also seem to have consistently low values in ntp.drift and >> handle timekeeping well. > > Does that matter? A good question-- the answer seems to be that it depends. > The RTC time is almost immediately overridden by ntpdate. The > drift is a systematic error that ntpd allows for. I would > have thought that the only significant issue, is whether the system > loses timer interrupts under load. There are limits to how rapidly ntpd will slew the clock via adjtime (); the smaller the intrinsic drift of the HW clock, the sooner any adjustment (beyond the initial stepping at system boot via ntpdate) will complete. This only matters to stratum-2 and higher systems-- anything with a primary reference clock (GPS/WWV/ACTS/etc) is going to sync to that and ignore the local HW clock entirely. -- -Chuck