From owner-freebsd-questions Thu Dec 16 17:53:34 1999 Delivered-To: freebsd-questions@freebsd.org Received: from dorifer.heim3.tu-clausthal.de (dorifer.heim3.tu-clausthal.de [139.174.243.252]) by hub.freebsd.org (Postfix) with ESMTP id 3407814D93 for ; Thu, 16 Dec 1999 17:53:30 -0800 (PST) (envelope-from olli@dorifer.heim3.tu-clausthal.de) Received: (from olli@localhost) by dorifer.heim3.tu-clausthal.de (8.8.8/8.8.8) id CAA11742 for freebsd-questions@FreeBSD.ORG; Fri, 17 Dec 1999 02:53:29 +0100 (CET) (envelope-from olli) Date: Fri, 17 Dec 1999 02:53:29 +0100 (CET) From: Oliver Fromme Message-Id: <199912170153.CAA11742@dorifer.heim3.tu-clausthal.de> To: freebsd-questions@FreeBSD.ORG Subject: Re: softupdates cont'd... Organization: Administration TU Clausthal Reply-To: freebsd-questions@FreeBSD.ORG MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: TIN [version 1.2 RZTUC(3) PL2] Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Jonathon McKitrick wrote in list.freebsd-questions: > Well, softupdates are up and running for real this time ;-) > Has anyone found any limitations, or circumstances when they are > undesirable? As i understand it, the negatives are minimal: > > 1. More memory is used This is true. > 2. The FS _may_ be prone to corruption in rare circumstances Haven't experienced that (and we're using soft-updates on a lot of boxes, some of which are under quite some load). However, there are two points to consider: - When files are revode, their space is not marked as free immediately, but after some "sync period" when the metadata is written back to disk. This can be up to 30 seconds (you can watch this with "df"). This can be a problem when you do a "make installword", for instance, and your root filesystem doesn't have enough space to hold twice the stuff in /bin and /sbin -- It will just run out of space, and you could end up without having a /bin/sh anymore or something like that, which is a bad thing, of course. Even worse, there have been reports that the system could crash (panic) if the space on a soft-updates-enabled file- system overflowed. I don't know if this problem has been fixed (never happened to me anyway). For the above reasons, it is in general recommended _not_ to enable soft-updates on your root filesystem. It wouldn't help much anyway, because there are usually not many write accesses to that filesystem (provided that you have /var and /tmp separately, of course, which is always a good idea). Mounting / with the noatime option is usually enough, or even read-only if you don't mind re-mounting it each time you have to change something in /etc. - When soft-updates is enabled and the system crashes (e.g by a power failure or a kernel panic), you will lose files which have been re-written within the past 30 seconds (they will be there, but the size will be zero). Without soft-updates, there usually is still some content left from such files. > Has anyone found the system sluggish during makes (more than without > softupdates) or otherwise limited during some particular activity? I experience such slugginess once on an IDE-only system without UDMA enabled (but with soft-updates). Enabling UDMA in the wdc driver fixed it. Regards Oliver -- Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany (Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de) "In jedem Stück Kohle wartet ein Diamant auf seine Geburt" (Terry Pratchett) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message