From owner-freebsd-performance@FreeBSD.ORG Wed Sep 3 11:38:06 2003 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E715C16A4BF; Wed, 3 Sep 2003 11:38:06 -0700 (PDT) Received: from pop018.verizon.net (pop018pub.verizon.net [206.46.170.212]) by mx1.FreeBSD.org (Postfix) with ESMTP id E143743FEC; Wed, 3 Sep 2003 11:38:05 -0700 (PDT) (envelope-from cswiger@mac.com) Received: from mac.com ([68.237.14.199]) by pop018.verizon.net (InterMail vM.5.01.05.33 201-253-122-126-133-20030313) with ESMTP id <20030903183805.TSH11703.pop018.verizon.net@mac.com>; Wed, 3 Sep 2003 13:38:05 -0500 Message-ID: <3F5634FE.9080303@mac.com> Date: Wed, 03 Sep 2003 14:37:50 -0400 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 X-Accept-Language: en-us, en MIME-Version: 1.0 References: In-Reply-To: X-Enigmail-Version: 0.76.5.0 X-Enigmail-Supports: pgp-inline, pgp-mime Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Authentication-Info: Submitted using SMTP AUTH at pop018.verizon.net from [68.237.14.199] at Wed, 3 Sep 2003 13:38:04 -0500 cc: freebsd-hackers@freebsd.org cc: freebsd-performance@freebsd.org Subject: Re: 20TB Storage System (fsck????) X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Sep 2003 18:38:07 -0000 Max Clark wrote: > Ohh, that's an interesting snag. I was under the impression that 5.x w/ PAE > could address more than 4GB of Ram. It can. PAE lets the hardware address more than 4GB of RAM, but that doesn't change how much memory you can give to any one process: a 32-bit process still has a 32-bit virtual address space. > If fsck requires 700K for each 1GB of Disk, we are talking about 7GB of Ram > for 10TB of disk. Is this correct? Will PAE not function correctly to give > me 8GB of Ram? To check 10TB of disk? Another thread suggests that the maximum amount of memory actually available for a 32-bit process to use under FreeBSD is a little less than 3 GB. > Is there anyway to bypass this requirement and split fsck into smaller > chunks? Being able to fsck my disk is kinda important. Sure. Create multiple filesystems rather than just one, and use symlinks to make the directory namespace fit your needs. I don't know enough about your tasks to give you really specific advice, but I'm wary of the write-performance hit from putting too many drives wide in a RAID-5 (or -5,0) configuration. If you can split up your data by role or typical access pattern, you might well be able to identify some chunks that will be read-mostly (and RAID-5,0 is a good fit) and others that will be read-write or even write-mostly (and thus should be on -1,0). You can also tune other things like blocksize, # of inodes, and so forth more appropriately for each filesystem. -- -Chuck