From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from racke.linbit (chello080108047253.34.11.vie.surfer.at [80.108.47.253]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.linbit.com (LINBIT Mail Daemon) with ESMTP id 3AA2A2DDC153 for ; Sun, 21 Sep 2008 01:19:39 +0200 (CEST) Date: Sun, 21 Sep 2008 01:19:38 +0200 From: Lars Ellenberg To: drbd-dev@lists.linbit.com Subject: Re: [Drbd-dev] New Features: write-back cache mode Message-ID: <20080920231938.GA16320@racke> References: <48D3378E.3020201@gmail.com> <20080919155343.GD9779@soda.linbit> <91a37e890809190919g5a746367g54e76d36e1a825f6@mail.gmail.com> <20080919221339.GB15916@soda.linbit> <48D42783.1050403@gmail.com> <20080920131821.GB16149@racke> <20080920134827.GD16149@racke> <48D5818C.1030703@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <48D5818C.1030703@gmail.com> List-Id: Coordination of development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, Sep 20, 2008 at 05:04:44PM -0600, Morey Roof wrote: > This is pretty much what I was thinking. For the btree, generations, > and ref-count a good example to look at is how btrfs (This is the other > project I have started to mess with) works. The design is very > efficient and I think we could use a very close match for our setup. I > haven't read the paper you sent yet but will get to that today. > > Let me know how you would like to start and I can start working a proof > of concept and we can see how to go from there. I still think that should be implemented as a generic device-mapper write-back target, not as part of drbd. there is already some caching target out there somewhere, using small local low-latency disks as cache for higher latency "remote" iSCSI or GNBD disks. At least I read something like that on one of the linux thin clients projects a while ago. I did not look at the code, and never used it, though. a 10 second google suggests that http://www.acis.ufl.edu/~ming/dmcache/ is what I mean. maybe you can use that as a starting point, and point it to a ram disk as cache? -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed