Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751072AbWHBC3I (ORCPT ); Tue, 1 Aug 2006 22:29:08 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751075AbWHBC3I (ORCPT ); Tue, 1 Aug 2006 22:29:08 -0400 Received: from smtpout.mac.com ([17.250.248.175]:11475 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S1751074AbWHBC3H (ORCPT ); Tue, 1 Aug 2006 22:29:07 -0400 In-Reply-To: <44CFE8D9.9090606@mauve.plus.com> References: <20060731175958.1626513b.reiser4@blinkenlights.ch> <200607311918.k6VJIqTN011066@laptop13.inf.utfsm.cl> <20060731225734.ecf5eb4d.reiser4@blinkenlights.ch> <44CE7C31.5090402@gmx.de> <5c49b0ed0607311621i54f1c46fh9137f8955c9ea4be@mail.gmail.com> <5c49b0ed0607311650j4b86d0c3h853578f58db16140@mail.gmail.com> <5c49b0ed0607311705t1eb8fc6bs9a68a43059bfa91a@mail.gmail.com> <20060801010215.GA24946@merlin.emma.line.org> <44CEAEF4.9070100@slaphack.com> <44CED95C.10709@slaphack.com> <44CFE8D9.9090606@mauve.plus.com> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <0DA0B214-50BC-4E20-A520-B7AB121BB38B@mac.com> Cc: David Masover , David Lang , Nate Diller , Adrian Ulrich , "Horst H. von Brand" , ipso@snappymail.ca, lkml@lpbproductions.com, Jeff Garzik , "Theodore Ts'o" , LKML Kernel , reiserfs-list@namesys.com Content-Transfer-Encoding: 7bit From: Kyle Moffett Subject: Re: Solaris ZFS on Linux [Was: Re: the " 'official' point of view"expressed by kernelnewbies.org regarding reiser4 inclusion] Date: Tue, 1 Aug 2006 22:29:20 -0400 To: Ian Stirling X-Mailer: Apple Mail (2.752.2) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1447 Lines: 28 On Aug 01, 2006, at 19:50:49, Ian Stirling wrote: > You probably don't actually want to flush the cache - but to write > to a journal. 16M of cache - split into 32000 writes to single > sectors spread over the disk could well take several minutes to > write. Slapping it onto a journal would take well under .2 seconds. > That's a non-trivial amount of storage though - 3J or so, 40mF@12V > - a moderately large/expensive capacitor. IMHO the best alternative for a situation like that is a storage controller with a battery-backed cache and a hunk of flash NVRAM for when the power shuts off (just in case you run out of battery), as well as a separate 1GB battery-backed PCI ramdisk for an external journal device (likewise equipped with flash NVRAM). It doesn't take much power at all to write a gig of stuff to a small flash chip (Think about your digital camera which runs off a couple AA's), so with a fair-sized on-board battery pack you could easily transfer its data to NVRAM and still have power left to back up data in RAM for 12 hours or so. That way bootup is fast (no reading 1GB of data from NVRAM) but there's no risk of data loss. Cheers, Kyle Moffett - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/