From owner-freebsd-hackers Tue Jan 5 21:54:13 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id VAA19452 for freebsd-hackers-outgoing; Tue, 5 Jan 1999 21:54:13 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from lamb.sas.com (lamb.sas.com [192.35.83.8]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id VAA19445 for ; Tue, 5 Jan 1999 21:54:11 -0800 (PST) (envelope-from brdean@unx.sas.com) Received: from mozart (mozart.unx.sas.com [192.58.184.8]) by lamb.sas.com (8.9.1/8.9.1) with SMTP id AAA02443 for ; Wed, 6 Jan 1999 00:53:43 -0500 (EST) Received: from dean.pc.sas.com by mozart (5.65c/SAS/Domains/5-6-90) id AA24227; Wed, 6 Jan 1999 00:53:42 -0500 Received: (from brdean@localhost) by dean.pc.sas.com (8.9.1/8.9.1) id AAA20063; Wed, 6 Jan 1999 00:53:42 -0500 (EST) (envelope-from brdean) From: Brian Dean Message-Id: <199901060553.AAA20063@dean.pc.sas.com> Subject: Filesystem overflow ... can it be done? To: freebsd-hackers@FreeBSD.ORG Date: Wed, 6 Jan 1999 00:53:42 -0500 (EST) X-Mailer: ELM [version 2.4ME+ PL43 (25)] 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 Hi, Once a filesystem fills up, is there a way to have it "overflow" into another filesystem or area of storage? I want build a machine whose filesystem is memory-base, i.e., MFS_ROOT, where root, usr, var, etc, etc, is all memory based. However, I expect a goodly amount of temporary data to have to be dealt with in /tmp, but not all of the time. The primary reason for this is for fast data and program access. The machine could be booted with a BOOTP kernel, and everything downloaded into it's MFS when it comes up. The problem is that /tmp can fill up at peak times, because I can't put enough RAM in the machine to cover the expected maximum. I would be willing to lose performance in this case by having my /tmp overflow onto disk-based storage when necessary, but I wouldn't want to use disk storage all the time. For a long time now, I've used /tmp as a memory based filesystem, and the rest of the OS on disk with good performance results. I'd like to experiment with putting more of my heavily hit code into MFS and maybe take this to the extreme end of the spectrum of having everything in MFS, while still leaving enough RAM to run my processes. Some of my questions are: 1) Can nearly the same results be achieved by dedicating large amounts of memory for disk buffers? 2) I don't like the idea of consuming RAM with programs in the MFS, only to get loaded into RAM again to be executed. Gzipping my executables will help, however, this will increase the activation time, and I don't want to go to all this work to have performance lost by decompression. Maybe the answer to this would be covered in part by the first question? 3) Is this even doable with the filesystem technology in FreeBSD? A while back I remember discussions about stackable filesystems which I think might be relevant here. Thanks for any help and suggestions. -Brian -- Brian Dean Process Engineering brdean@unx.sas.com (x5235) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message