From owner-freebsd-hackers@FreeBSD.ORG Mon Jun 30 14:08:18 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3F6DE37B401 for ; Mon, 30 Jun 2003 14:08:18 -0700 (PDT) Received: from fledge.watson.org (fledge.watson.org [204.156.12.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 53EAE43FEC for ; Mon, 30 Jun 2003 14:08:17 -0700 (PDT) (envelope-from robert@fledge.watson.org) Received: from fledge.watson.org (localhost [127.0.0.1]) by fledge.watson.org (8.12.9/8.12.9) with ESMTP id h5UL7fKJ002636; Mon, 30 Jun 2003 17:07:41 -0400 (EDT) (envelope-from robert@fledge.watson.org) Received: from localhost (robert@localhost)h5UL7fm9002633; Mon, 30 Jun 2003 17:07:41 -0400 (EDT) (envelope-from robert@fledge.watson.org) Date: Mon, 30 Jun 2003 17:07:41 -0400 (EDT) From: Robert Watson X-Sender: robert@fledge.watson.org To: Josh Brooks In-Reply-To: <20030630131951.L57224-100000@mail.econolodgetulsa.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: freebsd-hackers@freebsd.org Subject: Re: per-directory quotas possible on 5.x ? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 30 Jun 2003 21:08:18 -0000 On Mon, 30 Jun 2003, Josh Brooks wrote: > On Mon, 30 Jun 2003, Robert Watson wrote: > > > As you may have noticed in trying the vn-backed mechanism, there are some > > inefficiencies that turn up in FreeBSD when have large numbers of > > pseudo-devices, etc. The resizing problem is real, also, since we don't > > have online file system resizing. FWIW, a file system like HFS+ (which > > has a much more strict directory hierarchy) would lend itself to directory > > quotas much more. A port of HFS+ to FreeBSD was recently posted to > > freebsd-fs. > > Thank you for your very informative response. I am curious, what sort > of inefficiencies do turn up when you have large numebers of pseudo > devices ? > > Do you have any comments on a system running, say, 100 vn-backed mounted > filesystems ? 200 ? (presume moderate to heavy activity in each ...) I've observed two problems when using large numbers of pseudo-devices: (1) Hard upper limits on the number of such devices that can exist (I don't remember the current limits, but on -STABLE I seem to recall it's around 512). (2) Increased chances of a deadlock if you have lots of vn backing files in the same directory and you perform directory operations on the directory. This has been observed on -STABLE with a few hundred active chroots on vn-backed devices in jails. There have been some mitigating changes in -CURRENT recently that decrease the chances of this happening. The -STABLE workaround was to put each backing file in its own subdirectory if the problem occurs on your system with your workload. On -CURRENT, you can also use the GPT partition layout which makes it possible to have a lot more partitions on a disk than the BSD label format or MBR. Using disk partitions makes things a little more difficult to resize, but not hugely more, and avoids going through a file system loopback, improving performance (and eliminating the chances of (2) above). Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Network Associates Laboratories