From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cory Coager Subject: Re: support for external persistent cache Date: Wed, 19 Jan 2011 12:29:07 -0500 Message-ID: <20110119172907.GA1342@erebus.underworld.local> References: <4D365BE2.9020300@gmail.com> <20110119155211.GA31671@erebus.underworld.local> <20110119162941.GA32537@erebus.underworld.local> <20110119170252.GA891@erebus.underworld.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Roberto Spadim Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Wed, Jan 19, 2011 at 03:15:40PM -0200, Roberto Spadim wrote: > hummm.... > thinking again..... > > what?s the today raid1 problem? > it?s based on minimal disk size > for example... > /dev/sda 1gb > /dev/sdb 1tb > we can have a 1gb raid only > > what you want is: > 1tb raid0 > with a automatic /dev/sda to /dev/sdb write > > > could we call this raid0-cache? > i think we could implement it in raid.... > > check this fuse (filesystem) implementation: http://www.furquim.org/chironfs/ > it?s based on filesystem (ok it?s a raid1, not a cache like, but?s > limited to max filesystem size, not the minimal filesystem size... ok > it?s not secure to use it since small filesystem don?t have all > information, but?s nice) > > anyone want to make raid0-cache implementation? I have two comments on this. I don't think the cache device should be the same size as your disk storage. It should be a small cache size similar to hardware RAID. Also, we'd need a way to flush the data from the cache device on bootup.