From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Write intent bitmaps Date: Fri, 19 Jun 2009 12:16:09 +1000 Message-ID: <19002.62697.475588.28776@notabene.brown> References: <20090608021026139.GMOD14139@cdptpa-omta02.mail.rr.com> <18989.6010.582386.812296@fisica.ufpr.br> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: message from Carlos Carvalho on Monday June 8 Sender: linux-raid-owner@vger.kernel.org To: Carlos Carvalho Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Monday June 8, carlos@fisica.ufpr.br wrote: > > >5. What happens if the bitmap is lost or the external drive fills up? > > No idea. If the bitmap is lost, it is just as though you didn't have a bitmap (or as though all the bits in the bitmap were set to one). The drive filling up is not relevant. When the bitmap is in a separate file, the file is preallocated to be the right size. > > >If so, would ext2 probably be the best choice? > > That's what the man page says. I find it strange since if it's a file > the filesystem shouldn't matter. Neil? The way that md writes to the bitmap file is not entirely portable across different filesystems. As the man page say, it is known to work for ext2 and ext3. Either is a fine choice. A new filesystem interface is being introduced in 2.6.31 as part of the swap-over-NFS work. I might end up using that to write to bitmap files, as it has the right characteristics. But that is very much in the future. NeilBrown